Need device to charge ipod/etc from AA batteries

[SoulAssassin]

I'm looking for something like this but something that will take a female USB instead of an ipod specific cable. More and more stuff can be charged via USB these days so I'd rather have one device that can act as a backup for everything if possible. It should be able to run the ipod off the batteries and not just charge when it's off. Should run off AA not AAA or 9V.

Anyone have a recommendations?