Those rubber pad arms are the newer type and difficult to find as there were not near as many produced. They tried to band aid the carb again with that fix instead of the ball.
You can try sending a PM to @Mike in NC as he recently posted a big parts find and may have something in there for you. He never mentioned if he was going to sell anything or not but worth a try.
A product called Seal-All will stand up to the fuel or Yamabond sealer to try and glue it .
Since I'm always working on bush fixes for unobtainable things, I was looking at the Kohler carb float valves. They have a rubber tip on them which is about the same size. Never tried it yet but if it can be cut off clean and flat, then poke the point (may need to be sanded or cut a little) through the arm hole, Use a solder iron or something to melt the rubber to lock it in the hole.
Small RC check valve or valves in the fuel line before the carb?
Changing the diaphragm body to a ball type. It will bolt right on