I’ve got an AA flashlight labeled Small Sun ZY-C41. I just tried a 14500 in it and it melted the switch, so I guess its no good for li-ions. I’ve thrown in a li-ion driver for now, but I’d like to keep the AA option if possible.
Yikes! I don’t know of any really good driver options, unfortunately. Hopefully someone will come along who can help you. I guess I should also say “Thanks for taking one for the team” since your “testing” might save others from even worse. 
https://www.fasttech.com/products/0/10001750/1127407-12-aaaaa-5-mode-800ma-linear-booster-led-flashligh
Reviewers say works great with li-ion.
In all honestly I would probably just buy a Sofirn SF10 with free shipping.
Thanks, I’ll give them both a try.