Sounds like the milling setup on a Walker Turner. I don't think you'll find what you're looking for. Both ends of an adapter like that would be too big for the threaded collar to fit over. I made a replica of the original for mine. It's just a milling cutter holder with a shoulder for the collar to bear on, and the JT33 taper on one end. Mill holder is just a 3/8" or 1/2" hole with a setscrew.