Ok this one sounds interesting... http://www.xtrememac.com/chargers/micropack_submit.php
As for all ext batt packs it's better if you can possiblely actually buy them try it and then take it back. I've been able to so far avoid buying these because of my habits but there are times were I could see running into a batt problem. So far the USB power adapter has been the best solution.
Depending where you are Fry's has the BTi ext batt. I don't know if it's 1 or 2 though but at least you can try it and if you don't like it you can take it back