http://www.fvd-web.com/
I could be all wrong, but I ordered a catalog from them and they had really good prices on sets... and there's a choice of factory standard (cheapest), cross-drilled (more $) and slotted, which are evidently the hot new way to stop a Boxster fast ($$$)
Call them and ask for your specific model.
BTW- I also see sets of brand new discs on Ebay that should work, and they're reasonably priced.