We have a juicer mini that we power our synth with during music rehearsals so we're not having to run cords everywhere all the time, and it's pretty solid. It won't run the whole sound cart, but if stuff happens, it's on our synth cart and we can at least power him through a bass amp and the juicer mini which ride on the bottom shelf on his cart.

The full blown juicer should be a pretty great option, just not very cheap at all.