Maxboost Electron External Battery Pack
USB battery packs are a dime-a-dozen, but this is the one I use. It has excellent battery performance, holds its charge for long periods on inactivity, has a simple indicator, and even has a built-in flashlight.
It’s always ready to go in my Chrome Bravo backpack. When traveling, this is what you want for those long overseas flights to keep your tablet and any other entertainment going strong.