Thanks for everyone's help! I have retrieved the broken sheave.
Nice work!
For a 16mm shaft, I would order 316 stainless from McMaster and cut to length yourself, should be a few minutes work w/ a hacksaw. PN 1335T56 for example
The Selden sheaves are beyond sloppy even when new….I was definitely unimpressed when I bought new spare sheaves plus a new axle together. 3rd world machine shops frequently great at basic stuff like this…..