I found a match at my local Ace Hardware store, back with the exotic nuts and bolts in the pull out drawers. It was listed on the pull out drawer, as I recall, as an internal "C" ring clip, it was the smallest one in the drawer.

I gave up on the circlip in the wedge and bought a modified eccentric, as I described above. Before I gave up, I purchased a replacement circlip from Cannondale through my local bike shop because I could not find a spec for replacement. Turned out to be the same one available at the hardware store.