We've bowfished using spotlights off a battery. It's legal and it works just fine. Sometimes it seems like you can see more fish without the genny running. The generator is much more convenient tho'.

I also use a hawglite on my bow. It has a on/off pressure switch. Right now they're powered by a 9volt battery which works good if you don't try to use it as a flashlight. We'll be testing a different battery pack for them down at the World's shoot.(supposed to extend battery life to several hours of straight use)
The hawglite is awesome for the bighead carp.
http://www.razorbackoutfitters.com/index_files/page0012.htm

The club gets these for a special price. We're out of them right now, but we are ordering more.