If that doesn't work, you can always call John Berget. He collects good (as in no more then 2 or three heat cycle slicks and rains from all the major SCCA nationals in the midwest and northeast) and resells them.
For example, a set of front and rear drys for an FC from him cost about $270 including shipping to your front door. Call him and tell him what you need and if he has them in stock, you'll see them in about a week.
Berget Tires (262) 740-0180
We got several sets from him in past years including a SINGLE heat cycle set from the SCCA runoffs.