Glad you figured it out.I found some 6mm snap rings at Hobby Lobby and they work very well.
However the snap ring tool is a bit of a mystery with these small snap rings. But I think I got it figured out, it just opens them enough to get the cuff through.
The cuffs lay flat with out any rough egdes sticking up.
I'll post pics later.
Found the cuffs on Esty.