I knew someone in that position who ended up having to make their own
As I remember, they obtained some very firm rubber, cut it out of a
sheet
(cant remember but they may have laminated it, ie: glued together 3 or
5 thin layers) and turned
it to the correct diameter and smooth running surface on a lathe.
This part was quite time consuming as the rubber had to be frozen
solid
overnight to be hard enough to turn, and when you start doing
turning it gets hot (and softens) rather quickly.