Audi themselves do not make the bar, it will usually be made by a reputable third party supplier anyway, often I believe it is a German company Westfalia who supply VAG cars but I could be wrong.
Go to a well established independent towbar outfit who supply a good brand such as Westfalia. You may even be able to get the OEM bar just under a different name.
Also, make sure you pay the extra for the dedicated wiring kit. Westfalia will probably make the dedicated plug in kit which will plug straight into the car and not require any electrics to be chopped and joined. Again this will possible be identical to OEM. Sometimes these even have the Audi part numbers on them.
If you use a proper Westfalia dealer, they will likely have access to a coding machine or be able to take it to the local Audi dealer on your behalf.
The end result should be the same as OEM just significantly cheaper :)
Let me know how you get on.