Large chair castors?

I bought a large recliner chair and was assurred by the retailer that it would move easily on carpets. It does not. The retailer said that had I told him I had Indian rugs' he woulod no0t have sold me the chair.. The fittings on the bottom of the chair are like upturned rubber(?) saucers held in positioin by bolts.
Is there anwhere where I may buy castors with threaded bolts and nuts? I had a similoar problem years past with a HSL recliner and eventually HSL supplied castors with a thread and nuts.