http://www.ebay.it/itm/121327400104
I think it comes with a plastic base and in a metal bulb holder - BUT
I *think* it is a T15 bulb stuck in a bulb holder and you get the bulb holder with it, but not sure.
The Audi P/Ns are:
pre-facelift 4E0945981 bulb with black socket
facelift 4E0945981A bulb with grey socket for back-up light 12V16W
Probably the same part anyway?