Thanks for the info, and the bearing picture. I should be able to have my brother machine something similar to that for me. As you mentioned earlier, the original top plate is not really a bearing at all, and I would like to improve it.
My rudder shaft doesn't seem to enter through the cockpit floor at as much of an angle as your's, or maybe I just have never noticed. I will have to look, next time I go to work on the boat.