Hi,
Really 1.4 volts?
I always wondered why the dollar stores didn't have 1xAA or 1xAAA flashlights
...
did a bit of searching and I see compact joule thief isn't too hard to build



and that you can just get one from solar garden light



so no reason the cheapest flashlights couldn't have one of these
4 legged integrated circuits joule thieves
...
I also figure one ought to exist already that clips onto a battery
and it almost does , the Batteriser
naturally lots of smoke and mirrors and no actual product yet