I have the same problem. I cracked open the remote and it looks like the replacement battery is a US503759 A8H. Luckily the battery is commonly used in cell phones and can be ordered online for $21.00.

[Link: worcell.com]

The problem is that it has a small circuit board with plug soldered to the tabs. That is a bit above my DYI and I may need to pay someone to attach the board to the new battery. Once that is done, it should be plug and play.