Gus,
Very nice illustration.
I have never seen those steel washers for sale as new/reproduction. Try a Parts Wanted ad in the Swap Meet.
If someone would measure the inner and outer diameter (I have none in the open to measure), you could check McMaster-Carr and/or Fastenal to see if they have something.
By the way, in most of the tail-pieces that I have taken apart, there was a rubber seal not a felt seal. What is the seal-material in the gasket set you have?
Good luck,
