It's 1-1/8" top bearing? Maybe an option in the below link will help for a top cover than you can use some regular carbon spacer.http://www.cannondaleexperts.com/Headsets_c_64.html
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Check out this page. There are several headset top bearing covers that should fit over the bearing, then you can put a regular carbon spacer, or just slam the stem right on top of it.
There might be cleaner alternative like you are looking for, Cane etc..but don't know the exact one for that frame.
I would be careful with Cannondale headset anything also, they are whacky with their sizing, particularly on the tapered 1.5-1 1/8" setups, bearings are larger than normal top/bottom on the outer diameters, inner ring diameter and race crown/fork shoulder smaller etc...They do not follow standard SHIS bearing sizes. I know my supersix upper sits slightly higher by 1mm than a normal bearing 1-1/8". It's a 7mm instead of a normal 6mm thickness I believe. So if you put a top cap that doesn't match up and have enough space underneath with the bearing height, there will be a larger than normal gap between the bottom of the bearing cover and the frame.
I know you are asking for spacers specifically, any old spacer should work then for that matter...Ritchey/FSA, etc...but you will likely have to buy the entire headset just to get a thinner spacer.
But again, look closely at the top/bottom and how it matches up with the bearing cover etc...Cannondale is tricky like this.
Food for thought. Just went through this with a new frame, headset bearings and my Supersix frame bearings I was hoping to swap over....nada.