I'm borrowing a camera from my Mom that may help me to get the part # off of the MC w/o uninstalling anything.
in the meantime here is some info from the autohaas auction for the MC I bought. They don't currently have another but this may help you to track it down!
Item# 121473717921
Stock# 002449
Interchange# 541-50365
Purchase date 11/5/14
The 25.4mm MC that you need is also used on 07-13 TT that have the 3.2 engine.
The base 2.0 TT uses the same MC as the golf R which is 23mm.
The Centric MC that is 25.4mm is currently not in production. Which is what Centric direct told me on the phone yesterday.
8J1611021E
Its this part number. But was pointing out that its not just the TTRS that this part is used on. Also not found any aftermarket/Interchangeable part other than the Audi OEM part.
So end result is that 8J1611021E is the largest.