Often times if I'm crunched for space I'll just carry this weird multi-use charger gizmo I found deep on Amazon. (
http://www.amazon.com/gp/product/B00...ls_o04_s00_i00)
It'll allow you to charge 2 USB devices with a wall outlet, car cigarette port, 2 AA Batteries, or one 9V battery. I've used it all over the US for trips where I have to pack light, but I've never used it on anything but 120V.
My only complaint is that the amperage output is fairly low. It's so low in fact that I have to keep the screen on m iPad off for it to charge, but I'm OK with that annoyance for the convenience factor!