Agreed! This is the one I bought for a trip last fall: http://www.amazon.com/gp/product/B00DUKJ5CQ/

I only charged it a few times over two weeks, and still used my GPS and phone daily (though I kept it in airplane mode most of the time). A dynamo hub would be nice, but honestly a battery pack like this works fine for nearly all my needs.

Many of the cheaper units I've seen from no-name Chinese companies have bad reviews, so be careful when you buy.