I was looking for a used Graz shifter for about a year but ended up buying a new one from a online Audi dealer. They are extremely hard to find used. The best tip I could give is to watch EBay European sites to find one. They come up more often overseas.
Fran at RCR also sells a Graz shifter of his own design. It ends up about the same cost as a OEM shifter. It has a smaller profile though if that maybe important to you.