I had similar issue with my CAAD10 and couldn't find any from the various local shops that fit correctly. I wound up going wtih a Cane Creek. You can find what you need on their website and can buy it directly from them. They sell their headsets with separate upper and lower assemblies. You may have to buy the whole upper assembly but it wasn't terribly expensive and you get a spare bearing anyways.

You'll need to know various dimensions for your current headset (bearing angle, OD of cap your replacing, steerer tube diameter, etc.)