I have the Powermonkey Explorer, and it's fantastic! It comes ready with a small Nokia tip, and it fits very snugly. You can also use the tablet while it's charging.

The solar adapter is amazing, and will give you power from just a regualar incandescent light bulb. It works best outside though, so I usually just lay it on the dash of my car or something.

http://www.powermonkey-explorer.com/