At the risk of a hand-slap for cross posting (from the troubleshooting section), if you need a replacement disc clamp for the PR-7820 player (the rubber plate that goes to 'goo'), please let me know.

Blaine

Was going to post, this is a great piece to know how to make if you own one of these players.
I was going to try and figure it out back in the day but I did find a correct replacement, then sold off the player.
Thanks for posting this.