Like this one;
http://www.shopperschoice.com/item_i...ml?PID=2133188
I think the size of the battery is meant to be in cm and not inches, I doubt they would sell an ipod battery bigger than an ipod.
Here have a few different sized 3.7v 1000mah batteries.
http://www.batteriesamerica.com/ipod_batteries.htm (BP-iPODPHOTO actually looks like the most appropriate).