I have them, extra stong, nickel plated, and with extra timing marks to make dialing in the ignition timing easier on a modified motor. They are here: Supercharger Kit
You can get a decent used one from Alfa Parts Exchange in Tracy California. However all the original types crack eventually if used on a car with A.C. They crack where the keyway is. Mine will never fail.
Oh, and mine is over 1/2 pound lighter than stock.