I swapped out my original key fob to one recommended by another forum member. I can't remember who it was.
The new one is from LA Car Tech and is built almost exactly like the original. I will have a post about it in "My Journey with my 2006 Roadster Svengoolie" thread.
Like the original, it was a pain in the butt to open! It does come with a blank transponder, circuit board and battery (single) already installed. I used my original parts.
Here's a couple of pictures comparing the both fobs.