I got a pair here:
Nineapart Home - Used Porsche Parts - Porsche Recycling Facility
They are a disassembler in Toronto and I paid $60 each for them plus shipping.
I don't think you can buy just the seals from Porsche. It isn't shown as a separate piece in my catalog. Kinda sucks to have to buy a whole headlight because the rubber seal rotted away.