Making brake cylinder pistons isn't rocket science. A piece of aluminum round stock, a lathe, and some emery cloth for final sizing is all you really need. After I honed some very scarce wheel cylinders for a big GMC about .010" oversize to eliminate some pits, I just made pistons that fit the new bore size. NAPA open stock cylinder cups had plenty of expansion to fit the slightly bigger bore. New cylinders were available- - - -for $96.00 each- - - -two per hub!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!