Ok I learned something about the non-removable batteries. There's a new law in the US called Reese's Law that puts a bunch of annoying restrictions on any device that uses coin or button cells. They have to be difficult to remove from the device, to stop little kids from taking the cells out and eating them (eating batteries is very dangerous). Reese of Reese's Law was an 18 month old infant who died after eating some coin cells, so now lights like the Black Diamond Flare are discontinued, and the Streamlight Nano (used four LR41's) is replaced by a version that uses the silly AAAA cell instead of button cells. A nuisance, but think of thE chIldrEn!!1! So we will see yet more needlessly rechargeable devices with non-removable batteries, that turn into e-waste when the batteries crap out.

I'm guessing (don't know) that the Walmart light that I linked further up is unaffected by Reese's Law because you need a screwdriver to get the batteries out. I would expect the Photon Freedom to be affected but my contact at photonlight.com says they haven't heard about this. The Photon II has screws so might be ok.

I've been wanting to try making an ultralight headband for a 1AAA handheld light, with the light on one side. I know that some people do that with the Nitecore Tube. I wish the L shaped format was more popular. The Lumintop one I linked further up looks discontinued, and got bad reviews on BLF.

I need to check whether the Walmart light has any parastic current drain, since I think the on-off switch is electronic.

Re battery availability, I was in NYC during the several day blackout in 2003. AA and D batteries were sold out in the local shops almost immediately, but C, AAA, and 9 volt were plentiful. I was glad I had an AAA light with me, the classic Arc AAA with about 3 lumens. It was really bright enough for almost anything I wanted a light for.

I got a Wurkkos HD12 out of FOMO (it was on sale) but haven't tried it yet. I also have an HD10 which is 14500-only but has software that I like.

Added: oh yes, the dealer I got the NU05 from sent me another one, and its battery is also unhealthy though not dead like the last one was. It's definitely usable as an ultralight headlamp, with a beam similar to the Walmart light. I still can't recommend it though, do to crappy UI, non-replaceable battery, and high cost when it comes down to it. I'll do a more detailed writeup on a flashlight forum sometime.