Here is the one I bought:
Audi Key Fob Case/Blade
Everything was pretty straightforward, I ended up 'reusing' the plastic portion of the original fob that contained the immobilizer chip (since I only have one I couldn't risk destroying that chip). The board is a PITA to get out, ended up trashing the old housing to make sure I didn't damage the board. All in all the quality is pretty good though I think these are reproductions and not oem audi parts but it sure looks worlds better than how it looked before.
This how-to helped even though it is for VW: Smart Key FAQ
Ben, thanks for the part numbers... sorry to hijack the thread a bit!