Plastic Sub-base for Craftsman Router 315.17380

I have a Craftsman router, model number 315.17389, that I bought many years ago. I attached it to a router table and misplaced the sub-base. I have since removed it from the table and would like to use it as a free-standing router. I have searched all of the usual replacement parts sites but it says the part is no longer available. Does anyone know where I might get a used one from somewhere? It's a great router!