Well, you can use a collet which would be best, if you don't have one and don't care to buy or make one I'd think that dental adhesive may do the trick. For a cheap collet system, most economy tool places sell the alumiunim jaws for vices, if you get a thick enough set and drill the proper sized hole you should be able to use that as a split ring fixture. Slow I know but it would allow you to make a few and see how they do.