bobcen, as the old saying goes, "there is a collector for everything", ....... the problem is to find that collector.
Old porcelain and glass knobs and handles are usually "collected", meaning thrown into a box and saved, by dealers and refinishers of furniture "just in case" they find/purchase an item that is missing one or more of the original/period "pulls". I still have such a "box" with 15 - 20 such glass "pulls", ... porcelain, clear glass and green glass.