By specifying a 10cm length you are guaranteeing a very short runtime (10 minutes if you are lucky) and a light that is going to get hot enough to set your hands on fire. Not to mention the need to use exotic lithium cells that can handle such high discharge rates safely.
Practically this requires heat tolerant and high discharge rate cells, which means lithium iron phosphate or lithium manganese cells in 14500 or 16340 sizes. These aren't cheap or of high capacity. Which means very short usable times. The only lights I own that come close to meeting those criteria and can still run on ordinary lithium cobalt cells would be the Ultrafire U20 and the Trustfire R5-A3.
But both of those cost less than $30. I could easily devise a $500 device meeting those criteria but you'd be throwing money away unnecessarily.
Make the maximum length 15cm and things change a lot.
According to Manafont, the Mr.Lite LT3 is 9.65 cm long. According to Don's review it has excellent heat sinking, but it has a short run time on high. I don't own it, but this looks like a decent choice, especially if heat sinking is important.
I used to spend some time in those custom builder threads and it always amazed me how so many people would line up to buy these lights. If you listed your Ti Haiku for sale over there for $350, it would likely be sold in 15 minutes. It's not a criticism at all; if I had it I would do it too. But in my small circle of existence, no one casually tosses $200 - $500 (or more) away on a flashlight. I guess it's the pure indulgence of it I find facinating. Can anything be more superfluous than a collection of identical or nearly identical torches that . . . uhh, wait a minute - that's what I do but on a much smaller scale. Maybe we're not so different after all.
In my circle of existance anyone would love an excellent flashlight. But even if i would show that 200+ usd flashlight and offered it at 40usd there will be a lot of "meh" around. Good flashlights are not for everyone i guess those who do not appreciate them might as well donate for Japan and get the 9 led one along. If the find their smarphones lacking in lighting department.
It is one of the smallest 18650 flashlights. It is possible to get more lumens out of a smaller flashlight, but then it will heat up very fast, and the battery will not last very long.
Let me know how that works. The only thing I can see to complain about the Z1 is that they put the clip 180 degrees opposite the lens. So when you have it clipped to your belt the lens is pointing straight out away from you. Seems like it would be an easier carry if it pointed forward or rearward , not straight out to the side.
Well if you get one without build quality issues, the Thrunite Neutron 1C is under 4" and will put out over 300 lumens on a 16340. My Neutron 1a seems to put out over 200 lumens on a nimh and I have little doubt that it will do over 300 lumens on a 14500 and the 1C seems to use the same head. I would like my 1a if it didn't have the darn wobbly head. With a $500 budget, you could buy 9 of them.