If I was making it I would chuck a short section of rod into a drill and clamp the drill in a vise and run it at medium speed while shaping with a file or a grinder running in the counted direction. when I had the shape I wanted at the end I would split the ball with a cut-off or saw, and drill the holes for the cables, then saw off the rod. I have a bunch of lathes so I would actually machine it, but I used to make quite a few parts on a drill before I got the lathe. Some people use drill presses to do work like that, just be sure to respect that even a 1/3rd hp motor is not something to mess with. So lets say you are cutitng off by holding a hacksaw against a spining part. No problem, but stop before it cuts so deep there is any risk of a jam. That saw starts to whip around with you holding on, and it can hurt,, but it might help you to get a shallow groove then do the rest by hand.