Some camera batteries would work also. This one is protected, and is 700 Mah. amazon.com/OLYMPUS-Equivalent-Battery-Digital-Cameras/dp/B000XWYMB8/ref=sr_1_6?ie=UTF8&s=electronics&qid=1245942411&sr=8-6
I have seen them up to 1200 Mah, not sure about the protection on those.