That's scary, I wonder what mine is like after 36 years?
Guess I'd find out if ever I need a new 'screen.
Sorry I can't help with a supplier, though there is (generally) a healthier source of Classic replacement body parts out there these days. Hope you can source what you need, looks like you have a rebuild on your hands .. good luck with it
Classic.
Unless someone like yrm or Froggatt's do a replacement you're either fabricating it yourself or trying to find a good one on one that's being broken for parts.