I don't know the right answer Jim, but here is an ad from german guy who is selling S8 mirror cup and claims it'll fit both FL and pre-FL (years 1994 - 2003).
http://www.ebay.de/itm/ALU-Spiegel-A...71039721009%26
I'm not sure Audi ever sold cups only BTW. I think they only came complete with mechanism as one part for unknown to me reason.
Let us know when you find definitive answer to your question.