It's just a standard little 12v battery. You can order them online from many sources. They are rated by amp-hours. The only time you turn up the lightforce is when you are going to shoot. Take an extra with you and you can hunt till you drop.

Weedwacker
Indiana Predator Central

Some scientists claim that hydrogen, because it is so plentiful, is the basic building block of the universe. I dispute that. I say there is more stupidity than hydrogen, and that is the basic building block of the universe.

Frank Zappa