I'm after a left hand / passenger side window guide for a facelift 8L S3.
The part number is 8L3837439B
It's the rubber sealing strip that's attached to the metal window frame.
I would consider one from a 'breaking' 2dr A3/S3 guide that's still attached to the window mounting frame, perhaps even a whole door at the right price.
Price I'm prepared to offer will depend on condition and distance etc.