I got two of those external laptop batteries at Office Depot, Black&Decker. I can charge it in my car, or (untested and questionably) I could theoretically charge it with my crank Eton emergency radio that's supposed to charge your cell phone, too. The Battery unit has a mini USB power input, and both the Eaton and my car have adapters for that.
Admittedly, I got them for my gadget addiction, but then I got the fish.
Again, theoretically, if you got an adapter for
AC power through your DC cigarette lighter in your car (funny those still come standard, don't you think? They never lit my cigs very well, and I'd like USB or even a pre-adapted AC plug better now that I've quit) you could run an extension cord from your car.
I'm urban, more or less, and really don't expect too much need to generate my own elecricity, but I like to be prepared for anything. OK, mybe not so much be prepared as quell my paranoia....