Here's how we took care of charging several different cameras with different chargers. We carry a small 12v battery--the kind made for garden tractors. It costs about $25 and has enough capacity to get you down the Grand Canyon with power to spare, even if you use it (as we did) for topping-off rafts in the mornings and inflating air beds in the evening.
You see here a 300 watt Jensen inverter, which has two AC outlets. Everyone was able to plug into that when they needed to. We even re-charged our satellite phone on it.
The next picture shows how I carry the battery. That little 6-pack cooler is just the right size for the garden tractor battery. I wired-up a cigarette lighter outlet to the battery, and the inverter plugs into that--as can any 12-volt charging system.