I just purchased a 7960 mah battery with larger rear cover. Cover is shaped like the original and has antenna built in. 3g/4g works perfect and in the process of testing the battery life (just got the battery today). So far, it seems to be lasting MUCH longer than original...and original was pretty nice.
Here's the EBay link:
PS...don't know that it matters, but they sell them "carrier specific" as well. I got the one for a Verizon GN2...this link is for Sprint