Try Coilhose Pneumatic. They sell rebuildable American made regulators, along with the kits and diaphragms to service. If it’s an imperial sized unit, one of their kits will surely work.
I just found this via an unrelated google search. Do you still have the Devilbiss 432? Parts from a model 342, or 44643 will fit. DevAir can get you set up.
Id love to buy your pump if it’s feasible. I have rebuilt a few of these. I am in Texas.