The discs for the Porsche LSD's are different than the AUDI parts. The size was increased. (both od and thickness)
The p/n's are:
cup spring 928.333.555.00
inner disc 951.333.551.00
selective discs
1.9mm 917.332.552.10
2.0mm 917.332.552.11
2.1mm 917.332.552.12
I did some checking and they seem to be temporarily out of stock.
You could try these guys:
Motor Meister - Porsche Engine Rebuilder Carquip, Porsche Parts
Since the discs are 917 parts, they might have them.