Nitrile diaphragms and valves will outlast old fashioned rubber parts. Is your pump rebuildable? I opted to rebuild the pump on my '36 Plymouth with compatible parts rather than try and locate an assembled pump.
https://classiccarbs.com.au/index.ph...ump-Diaphragms
This thread has some replies from a vendor that would sell compatible parts or do the rebuild.
https://www.stovebolt.com/ubbthreads...&Number=962257