dvandom

It's not as "techie" a solution as an o-ring, but the way I learned to deal with too-big rings was to wind yarn around the palm side until the ring fit better. The yarn gives a little, so it'll allow the ring to be put on and pulled off, but it also provides enough friction that it isn't as likely to get flung around the room if you talk with your hands and make an exuberant gesture.