Is there a AA/AAA battery portable charger for Iphone/ipods?

I have looked everywhere but cannot find a portable charger for ipods/iphones that uses actual batteries rather than charging. I assume its possible since I've seen a chunky case for the ipod touch once that used batteries, and I'd honestly much rather have a portable charger that can charge up my device as many times as I want instead of one that needs to connect to a wall to charge itself after one or two charge cycles.

I'd plan on using it on the iPhone 4 and iPod Touch 4th gen, if that makes any difference