I purchased a "CREE C8 Green Light LED 300LM Hog Hunting Flashlight For Rifle W/Barrel Mount" off ebay for under $25. Very bright light. Solid beam. Can see objects very easily out past 100yds. I've shot a few times with it mounted to my barrel and it seemed to work fine. I will be using it here in a couple weeks while hog hunting!
I think that windfire is the same type of off brand light.