Sorry to hear of your turbo failure. My dad had exactly the same issue on his a3 8v with the same engine.
I'd be checking eBay personally. In failing that you could get a reconditioned unit. The main advice I would give you is try and get genuine Audi if possible, either new, used or reconditioned. As some of the aftermarket turbos have known to fail outside of their 1 year warranties.
Cheers
Steve