i was recently discussing with someone in second life a collar she was considering buying and she directed me to axsmar. after a bit of a dig around i noticed the more ergonomically shaped silver collar thats not a perfect round circle, rather it conforms to the wearers shoulders so the pressure is not just on two points.
i do have an eternity collar and i do love the idea of it but wearing it for any length of time is pretty painful. its heavy and its steel after all.
so this would be the way to go if your interested in having a proper collar. do look around too as they have very ingenious fastening and locking mechanisms. one collar design is made to go on an not to come off. it simply click shut.