Where to find pneumatic piston pump air cylinders?

No , But I can tell you the name of a guy that builds USA Compressors with USA parts and not that much higher than the china stuff,
He builds them , He sales them and he talks to you , In good English.
Its a garage compressor, Not a living room compressor,,,
I fill my great white and my small tank up to about 4800 PSI , In minutes, Not hours.
Mike