I'm very happy with this:
http://www.amazon.com/gp/product/B00...?ie=UTF8&psc=1, currently $16
I know, it's not AAA or AA batteries like you specified, but the battery pack is external and they're fairly inexpensive also. It has a charger, no need to plug into a usb port. The battery packs are built from 18650, superior to alkaline in just about every respect.