Well the bigger battery beats it right off the bat .
I'd carry the Sofirn and see if the weight or size bugs you.It will give you some thought as to whether 3 lumens works for you too . try it for a few weeks .
That’s the plan when the C01S arrives:
Ouch. I’m spoiled by Prime, could have another one tomorrow with free 1-day shipping if I wanted. 
Are you sure you’re not a little jealous that my order comes with free patience training? :laughing:
Haha, I’ve had plenty of “slow boat” experience too.
Happily, my LT1 just turned up much sooner than expected today, woo-hoo!
If you only judge by weight, it will lead you to the Photon:
I carried a photon on my keys for years.
then I tried a couple 10180 size, I found them finnicky and gave up on them
also tried a Pico Light, gave up on them when they needed new batteries
then I got into AAA, and stopped putting lights on my keys, or if I did, I used a quick release:
at that point I became aware of High CRI and started having Low CRI lights modified to N219b
I still love N219b. A High CRI LED is more important to me than the host.
My Spyderco Micarta Jester is 62mm. I believe you misunderstood how I carry those. They hang inside hooked on a corner of my pocket. Completely out of sight and do not hang far enough to interact with my keychain at all.
I have an Olight i1R on a neck lanyard right now, a Fenix E05 on my keys since 2014, and an old UltraFire B3 on my other set of keys (circa 2007). (And an S1R-II in my pocket, lol.)
Replaced the wife’s dead Nitecore Tube on her keys with an Olight i3E.
Some have mentioned them here, already, but I will second: RovyVon A series flashlights!
I carry one in my keychain and one in my neck!
Choose the body + the led + the configuration that suits you the most and get one, you won’t regret!
They have updated their UI and other things related to host material, battery and LEDs, so you won’t be disappointed if you get one 
Trust me! 
Phouton,
Here are some additional minimalist AAA’s lights for your consideration just in case you find the C01S large. Unfortunately none have built-in USB but I suppose you could always use a AAA cell with built-in charging.
From left to right -
Sofirn C01 (not S), Olight i3S, Lumintop EDC01 and DQG AAA Ti (covered w/wrap).
The DQG AAA Tiny is a Hi-Lo twisty, takes AAA or 10440 and is neutral/warm tinted; been banging around on my keyring (hence the wrap) for the past almost 10-yrs and I never notice it’s there.
I was about to pick up a TIP w/Nichia from Illumn after seeing that deal and realized right before buying that its rated to only IP54… no thanks.
Olight I1R, w/ usb charging
You want keychain, small, quick to use…If you can forego the usb charging you might take a look at a Slughaus Bullet
https://www.amazon.com/Bullet-02-Tactical-Smallest-Flashlight/dp/B01LZVZ38F
Let me ask the more obvious question If you have to charge your USB keychain light ...Isn't out of service during that time ? So your keys are now over there >>> by the charger >>> Over there >>>>
Sorry this thought to me seems VERY ODD... Because I have my wallet and keys connected .,,, that means me /my keys / my light and more importantly my ID,credit cards and CASH are separated ...No No NO !!!
Opening a light and dropping one out of the 3 million AAA's I have already charged ..or an alkaleak takes a whole 11 seconds.
Hmmm ODD. I don’t typically carry keys. I have the Olight i1R with a loop of paracord (guts removed) that is long enough to easley slide onto my wrist so that carrying/using it that way is an option. But the normal daily mode of carry is with that loop passed through a belt loop and then the light passed through the loose end and then the light hangs down a few inches into the front pocket. It can be held while still attached to the belt loop or just on and hanging hands-free. I only recharge it about once a month because it is not my primary light.
Jetbeam MINI-1 SS $16.99 at Illumn
https://www.illumn.com/flashlights/jetbeam/jetbeam-mini-1-micro-usb-rechargeable-light-cree-xp-g2-130-lumens.html
jon_slider That’s the thing, I’m not judging by a single factor like weight, although I highly prioritize it. I also don’t want single-use batteries. Plus the lack of a reflector or lens I think makes it less versatile. Totally agree that finicky lights are not worth it.
I think the best products are well-optimized in relevant features to maximize usefulness for a given purpose, rather than maximized in one or two specs.
chinooker Oh that’s a very nice knife size! The image made it look bigger.
riffraff A neck lanyard isn’t for me. But that’s a nice collection you’ve got.
MascaratumB Yes, the RovyVon A series are quite appealing… except for price! I just can’t stomach paying more for a keychain light than the SP33.
pc_light I appreciate the pic of all of them together! I have yet to test out the C01S, but I’m not sure if the differences between those AAA lights would be noticeable in practice.
Rat_Racer Yes, the Olight i1R is one of the best contenders. Sealed battery is maybe the biggest downside.
azj Thanks, but I’m not keen on non-rechargeable, button cells. That thing is next-level tiny, though! I like how they describe it as “tactical” haha
Boaz Quite right, but the charger is going to be a computer, which I’m virtually always in front of, so the keys will still be with me. This would be a bigger argument against a keychain USB drive since a file transfer can’t be interrupted, while charging a battery can. Despite this, my keychain USB drive has also proved itself useful to me. Also, in contrast to your use case, I sometimes go without cash or wallet, but not without keys. Different strokes for different folks! 
shirnask Great sale price! Unfortunately shipping kills it for me at 66% of the flashlight cost.
==
Now for some news!
I’ve come to terms with the very real possibility that what I’m looking for may not exist. So I reached out to Sofirn to see if they would be interested in making something meeting my requirements.
It turns out they have plans to make a tiny EDC keychain light! Check out this thread with a group buy interest poll and to discuss the design: [Group Buy Interest Poll] Tiny EDC keychain light done right - BLF/Sofirn-style!
Olight i3s
The C01S arrived earlier than expected: in only two weeks, and before the ETA, even though it flew from China, landed in Canada… then went to Germany and back??
First impressions:
- I love the SST-20 4000K CRI95 ! The light is so pleasant! I’m going to have a hard time using my Sipik SK68 which I thought was fine, but now… I did notice the slightly greener tint of the SST-20 at low brightness. Hopefully I won’t nitpick too much, but the color and “feel” of the light at full brightness is so nice. If anything it’s the contrast with itself at high vs low that causes any “discomfort”.
- The beam profile with the TIR lens is great! I thought I wanted something brighter than the SK68, but now I realize what I really wanted was a better beam profile: more light at a smooth spot for seeing details, and also wider spill for broad illumination. I haven’t seen much mention of the spill of this optic, since the hotspot is the most obvious part to look at. I really like how it provides wide spill that is enough for walking in the dark, while “saving” most of the light to point at objects and see clearly. I think this is a great balance and a good use of the lumen budget on a small light.
- I’m surprised at the usefulness of 3 lumens! It’s ample light for walking in the dark, and also great for really close up work without being blinded. It reminds me of my first childhood flashlight (incandescent 2X AA plastic body with no reflector), which probably wasn’t much brighter but chewed through batteries like crazy. This C01S lasts 25 hours on a AAA? Amazing. I can use 3 lumens liberally without fear of running out. Works great with the included light diffuser, which could be useful in a power outage.
- Given the above, now I really wish the mode order was Low-High. The usefulness of 3 lumens is reduced after being blinded by 100 lumens.
- The clip broke as I was trying to remove it. It suddenly sheared right off where the curved part meets the part that hugs the light. Maybe it was my fault for trying to pull it off. I should have pushed the clip off instead. Oh well, I wasn’t going to use it anyway. Still, it’s not the best feeling when something breaks within 5 minutes of opening a package.
- I worry about durability of the anodized color and wish I had a clear/natural option. After only one day on my keychain, if I look closely I can see the included metal ring has already scraped off the anodized paint on some edges around the keyring hole.
- The twist operation is ok with some flakiness. Specifically, once the light turns on, it must still be twisted further (~8-16 degrees rotation or ~1-2mm twist travel along the circumference). Otherwise in that region between turning on and being fully tightened, slight pressure on the head can cause it to flicker, or change modes, or turn off. This can be a bit frustrating since my instinct is to stop twisting once it’s on. It’s not a huge deal as I learn to use it, though I wonder if wear on the threads and O-ring will cause this to worsen over time. One concern for me was whether the head could come off unintentionally, but the pressure from the O-ring and the 4+ turns required to get it off have eased my worry. As for the operation, maybe my brain is a lefty, because with my right hand I often twist the wrong way.
- The size and weight (~26g) are surprisingly tolerable on a keychain. I still think smaller/lighter would be better, but I’m going to give this a try for a while. I’m finding the diameter might be more important than the length, and at ~14mm it’s not too bad.
None of this will be new to flashaholics, but I thought I’d provide a newbie’s first impressions. The C01S is definitely the nicest light I’ve used, and my favorite part is undoubtedly the emitter and optics. The lack of USB charging on a keychain light is somewhat mitigated by the capacity of a AAA, especially on 3 lumen mode. The size and weight are still under evaluation. Overall, I’m just really happy to have it with me while waiting for the perfect keychain light. I keep turning it on because… that light is just so pleasant to look at!
Agreed. The ultimate in utility, and simplicity.
An other version (slightly more Gi-normous).