I've tried my streamlight tlr-3 on my 22 compact and it worked out ok. There are some cheap weapon light options with decent output too, and if it's just a critter gun I'm sure you'd be fine with one of those..
Since they hold about 100 rounds, you could quickly light off the first of those flamethrowers, and then get a flash picture for subsequent shots in the dark,
Thanks for the suggestions. I was able to find a OLIGHT Baldr S Blue Beam 800 Lumens, on Amazon. It's currently on sale for $98.26. Really nice light and bright as Hell.