The diaphragm can be obtained Item
300390827996 here is a pic of the new and old ones. The "O" rings are also sourceable and if you PM your email I can send you a PDF file with step-by-step overhaul procedures and where you can source items required. Please note that cast iron FD had stainless steel diaphragm and the alloy types have silicon/butyl type due to metal reactions between steel and aluminium.
