Notice:
The advice given on this site is based upon individual or quoted experience, yours may differ.
The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.
It is called a T-ball retaining plug and is used on the mast end of shrouds on the C250. I would try calling Catalina or Catalina Direct first. This has come up before so I think some other C250 sailor will reply soon with a supplier.
Here is a link to a site that carries T-ball backing plates and the plugs. This is to be illustrative. I don't know what size the C250 uses. Basically there is a slot in the mast (or this "backing plate") . The shroud end fitting has a T-ball that fits in the slot. The "retaining plug" is pushed into the slot above the T-ball and keeps the T-ball fitting in the slot even as the shroud is loosened up for mast raising and lowering.
Notice: The advice given on this site is based upon individual or quoted experience, yours may differ. The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.