[HAM] Source of Upstop felt for older sharp keys?

[David Anderson]

I've replaced the upstop and downstop felts in my elderly CV manuals, 
and those repairs made a fantastic difference in how they feel and play.

However, the sharps still make that "diving board" sound when released. 
I know it's a pain to remove these keys and replace the felts, but I'd 
like to give it a try.

Trek doesn't sell the necessary felts, but Mike told me they were a 
woven felt, similar to the downstop felts he sells.

Does anyone know exactly what material I should be looking for?

Thanks,
David Anderson