If you drilled the original pin for a finger-sized split ring, it should be serviceable again, you just wouldn't have the "lock up" position that plastic disc and fixed pin provide. And even that shouldn't be too hard to fabricate/find (a piece of plastic that would do the same job)
I assume you have one working version to copy??
1984 Fast/Nicholson 345 "FastForward"
".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)