In the Uk these are..........
in addition to the Michelin & Pirelli Cups
Pirreli PZERO Rosso N1
Pirreli PZERO Corsa NO
Michelin PS2 N1's (as above)
& a Bridgestone NO rated tyre that I didn't get the name of as it was stated that they are too firm for the GT3!

But I don't believe Porsche will supply them as OE!