Congrats on the new boat! I would first try to identify the manufacturer of the main spar (mast) by its cross section. Try looking on rigrite.com or dwyer.com.
Once you find the manufacturer of the spar they usually group all of the parts related to that spar as accessories. If that doesn't work there is always the Morgan Owners site.
I'm sure someone else here at sailnet.com can help if you can't find the spar mfg.
Capngregg, thanks for your message. My mast was made by Kenyon; I've looked on rigrite but haven't found the piece I need. I'll give them a call though.