I picked up a Venom light two (?) years ago for less than $15 - works great.  Uses 1 AA battery for power.
https://www.venom-outdoors.com/product-page/nite-lite

I use the just the tip tip up lights, they are small, very bright, fit easily into my pocket and charge jigs as well as being awesome tip up and tip down lights. Www.justhetiplight.com 

This is a 4" flashlight in 365nm wavelength. Probably larger than what you're looking for but I've been pleased with it. Just make sure you don't shine near toward your eye as it can cause damage.  This sucker will make glow jigs super bright.

https://www.amazon.com/gp/product/B075GWKN83/