"Dave" wrote:
expecting to find some sort of serviceable pivot, be it just a pin or some
sort of bushing system. Hopefully inexpensively.

Yep. Here's a picture of one. Looks like a pivot pin you can get to.
http://ubu.ca/tanzer22/Musacenterboardafter.jpg

.... and here's the home page that may be helpful.
http://www.tanzer22.com/tpage.htm

Rick