Rs6 diffuser

Hi, I have a 2011 a6 c6 avant 3.0tdi quattro s line and I am looking to fit a rs6 style rear diffuser but I can not find one anywhere. Are they available? As I can only find them for pre facelift and se bumpers. All the places I have looked have said the diffusers they sell will not fit my car. So it would be a great help if someone could tell me if its possible to change and also what the difference is. Thanks a lot.

Anyone? I'm in stuck on what to do. Thanks in advance