Curtis quick drain

Mine started leaking after 20 years of service, not a bad service life for
something that I can replace for less than $10 at aircraft Spruce, or $14
from Sacramento Sky ranch. But since it is brass and looks to be in great
shape, I would just like to replace it's rubber seal. I thought it was an
o-ring, but it is a tiny rubber washer. I found what I thought was the
perfect replacement from Mc Master Carr, had to order 100 of them. Sadly
they do not fit. I asked the FBO guys next door and they said they used to
be able to order the seals but they can't get them any more. BTW the new
valve that I ordered from Spruce will be here next week.

Does anyone know of a source of just the seals?

Thanks for any info or suggestions.