early Vacuum Booster Relay Valve Diaphragm needed

[JGraf]

Does anyone have a Relay Valve Diaphragm (the small one) for an early sedan cast iron brake booster? Or any ideas to repair a torn one? I've already tried tire patches, RTV silicone, and various sealers without success, so now it's time to search for a replacement. It's H/C 52292, P/N 46448-568-671. A new one would be fantastic, a good used one would be acceptable to get the brakes back to their normal efficiency.