Bob, Google "cellphone batteries" and you'll get quite a few places to buy replacement batteries. Last year I replaced mine, it works fine but it does not have the snug fit of the original. But thats no problem as the replacement was half the price of the original.
Good Luck
Richard
There have been a lot of warnings about some of the replacement cell phone batteries, including an alert issued by the CPSC. The OEM batteries have some safety features internally to keep them from overcharging. A lot of the "cheap" replacements do not have the safety features and there have been a lot of reports of fires or batteries exploding.
There are non-OEM batteries that do have the same safety features as the OEM batteries, so not all are "bad". However, the problem arises of how do you really know since it's internal and not actually visible. And how are you going to prove a statement that the battery does meet the OEM safety specs.