If you are talking about the rubber part that is designed to swing out to initiate the kicking of the lever, most of them I have seen have an eclip on them. IF yours does, then perhaps you could put a small wedge in under the foot peddle portion and put the clip back on. If yours does not, the pivot is probably too worn and the only way I know to fix it is to replace it, or find a way to stuff something under it to make the pivot less free moving.