It seems that once parts like the 630-4668-402, 630-4670-402, 630-8874-402 "BELL / HIGH MOUNT / SCALE GP-9" go out of stock, they will not be produced or stocked by Lionel ever again unless they have a new production item that utilizes the same tooling. The idea has been floated that Lionel can only obtain complete assembled products from their manufacturers. To build their parts supply, Lionel actually disassembles units.
On extreme rare occasion, some vendors commission reproduction parts for these newer items, but generally speaking, with the initial relatively low volumes of products, this is far from being economically viable/sustainable.
