[Norretal]

I feel your pain David, my driver's side mirror did exactly the same. I settled for a "non auto-dimming" replacement after being told the cost of a new one. I got one for £15 from A8 Parts which was preferable to shelling out £100+ for an Audi part from a dealer.

I asked David if used one's were ever available and he said they're often no good by the time they get them in. Good luck with your quest