Jeff, that very part you are showing could quite easily done witout CAD/CAM from Aluminium just by turning the cylindrical part on the lath, slitting it on a mill and inserting a cut or milled part.
Fix the latter by bolting or by epoxy-cementing and curing.
Thanks AgX. I appreciate that it could be done that way but for several reasons it is not what I am interested in. For one I don't have a lathe. And as I indicated before I was really only interested in creating a small part which duplicated the tip of that piece. Lastly I really wanted a plastic piece. That is more in character with the cheap and/or old cameras that I seem to be obsessed with these days.