Aftermarket drilled disc's are easy to find and reasonably priced. I get mine from Cquence Brakes for around $65 each (
1999 Porsche Boxster Street Series Cross Drilled Slotted Brake Rotors | Cquence.net).
In regards to performance, on the street there is no noticeable difference, but I have raced on solid, slotted, and drilled disc's and greatly prefer the cheese grater's. They have a more consistent feel and cool better than the others.
The downside is that drilled rotors will crack when used on the track (street use is fine) due to the high temps and can't be turned or skimmed, so I end up replacing all of the rotors on each brake pad change. (
http://986forum.com/forums/general-discussions/43520-i-think-its-time-change-rotors.html).
Your mileage and preferences may vary.