Ultratac has a Nichia version of the K18, but I’ve only seen it listed for sale from hkequipment.
The brightest I know of is vinh’s (Skylumen) mod of the Lumintop Tool. Aka, the ToolVN.
Peak Eiger Ultra X? I have non-X and the output is a bit disappointing, but otherwise it’s a superb light.
The BLF 348 is sturdy, affordable, and has a decent tint, beam, and CRI.
But it has only one mode, and gets hot quickly when running a 10440. I recently purchase several for gifts from Gearbest for less than $9 each.
But it can run on a single cell, AFAIK. 
i’d be concerned about battery life - i would require a 1-5 lumen mode - not just ‘brightest’ - bright is easy but an LED can use up a 10440 in about 3 minutes on ‘brightest’
i use olights i3t copper for 10440… fun and the normal black i use a regular aaa battery… fun when u compare them on highest haha. compared to my olight s10/s1 baton that does 400/500 lumens the i3t whn using a 10440 is not far off from those lumens.
What is the advantage if at the highest level the runtime is only 30 minutes or less.
It’s brighter.
I like my Reylight Mini Pineapple a lot… There may be brighter 10440 lights out there, but it will do ~400 lumens at turn on, on high - and this is with a Nichia 219c, so the tint and CRI are great. On a 10440 light, you’re not going to get very much runtime on high - the thing that’s awesome about the Pineapple Mini is that it has a true moonlight mode even with a 10440. I use the moonlight mode at night all the time - it’s the perfect amount of light for in the house when all the lights are off, and the runtime is super long on this mode. As well, the medium mode is very usable on 10440. When you add in the solid copper body, and the great pocket clip, its the best 10440 light out there to me.
Edit: Rey is currently working on a Mini Pineapple with a tail clicky and programmable driver - I have the original, twisty Mini Pineapple. If banggood still has any of the original Mini Pineapple in stock (the Reylight website is sold out), there are coupon codes to get it for around $22, but it may be all sold out as he gets ready to release the newer model.
My two are the Thrunite Ti or Lumapower LM21. The Ti is a little smaller and nicer looking but I rather the LM21 because it’s a tad brighter and has a rear switch instead of a twisty.
Itp a3 eos
Have ordered a Sofirn C01s, but that is more of a aaa, light. Do we have any 10440 light, preferrably with USB-C that does hold its light for a while? A light that does not put all in on the power side for three minutes and then dies 80 degrees hot. Seems hard to find good lights in this category.
After a little research: https://www.reylight.net/product/reylight-pineapple-mini-aluminum/ seems quite nice! No USB-C, but a tritium slot instead, if you want a maximum of 3,6 Bq in your front pocket…
> reylight-pineapple-mini seems quite nice!
I agree, Rey offers excellent lights, and the one you found has my favorite LED, and a fully captive and deep carry pocket clip.
highly recommended
Great to hear! Have some l92’s in store for the sofirn, but will invest in a pine too. Just a higher threshold to have to buy a charger as well…
Ultratak K18 is my buy. Electronic lockout, great beam, useful to 50 feet/20 meters, BRIGHT (actually gets hot), good medium, and a useful low (but no moonlight mode).
My fave! Neutral White: 4000K CRI>95. Magnet in tail cap, excellent clip. Easy EDC and more versatile than a straight light.
Personally I don’t do 10400 though. AAA does everything I want. If I want more lumen I have other lights for that. Give up too much run time to gain lumen that aren’t really necessary for the close work that this is most useful for. (Fixing things, walking the dogs, etc.) Also, with the 10400 the incredible moonlight modes are sacrificed for a 5 lumen low. Unacceptable trade off for me. If 420 Lumen vs 220 lumen max is most important to you then the 10400 would obviously be the way to go.
Not the bestest, but the Olight IO3 is a pretty nifty AAA twisty, 3-mode, which has a pretty good high output, but not much variation between the medium and high, with li-ions.
I just use Eneloops in that one and they’re very hard to find these days. Wish I had bought more back in the day.
Chris
+1