"FSA orbit si" is what the website claims, not sure whether they mean FSA orbit IS or if this is a headset made specifically for Cannondale (presumably this is not a typo, and the latter is the case).

I had this problem with a Specialized S-Works once, and I had to call the company, only to find out that it was, in fact, a Specialized-specific FSA headset that you can only get throught Specialized.