Optio staff

[M. Demetrius]

There is a ready-made brass ball, hollow, that's called a "Hame Ball", and is used as a terminal for certain horse harnesses. Check with a saddle/tack shop. Will fit a certain sized shaft, but as the picture above shows, the shaft could be tapered. Remember, you're not going to have to hit anybody very hard, and if you want more mass, just fill the ball with lead most of the way. EZ.