you could buy an invertor, I've seen them as cheap as $20 for a single plugin. then you could pop it into the cigarette lighter when your on location and steal the juice out of your car.
Get a Lenmar MSC-1L Alpha Speed Charger. It charges Panasonic (and Sony and Canon and JVC) batteries about twice as fast as the regular charger, and it includes a DC car adapter. I think EVS sells 'em for around $69 or so.