If you want to try the smooth, hard quality of metal while still having something that could be easily (with care!!) cut off with common nippers you can purchase Teflon O-rings (as in the attached pics) from an industrial supply house for about one or two US dollars each. O-rings can be had in a variety of diameters and thicknesses (both inch and metric) and the black rubber ones sell for way less than a dollar apiece, the exact same thing that the sex shops sell for ten times as much.