Mike,
Go to EBAY and search for Williams replacement parts and spares, contact potential prospects web sites for what they have for sale or what you are looking for, they may be able to help you. About 6 months ago I had to replace a side frame on Williams PA diesel, purchased a used one and repainted it black. Trying to fix/repair these side frames is difficult since they fracture easily, I do not know if JB Weld will work as a permanent repair or short term fix, failure was not zinc rot.
John