How may I obtain these parts?

I have two sofas with two recliners each. In each of the four recliners; half of the outside shell of a bearing/wheel has been ejected from the chair. It is about 1 1/4" in diameter and is very much like a hard rubber tire which is lubricated on its inner surface. Could be a cover for a metal bearing. It seems to have something to do with the chairs ability to recline within its original footprint. I believe I can replace the parts if I am able to get them.