Funny how when you ask how to fix something, people suggest you get a new one! I'm too stubborn for that. I'm only on this forum because a lot of old Macs are worth the challenge to fix them (at least to me).

You wouldn't want any kind of glue like a rubber solution that retained a sticky surface, because it would collect dust ferociously.

You could try the kind of spray-on bandage you get in pharmacies - it dries to a flexible membrane. I'd first check what kind of solvents might be in it, and avoid anything that could melt the existing membrane, which I'm guessing might be neoprene. But since it's presumably harmless to human skin, it's most likely an alchohol. DISCLAIMER - just speculating.

Have you looked at audio or vintage-audio forums for tips?

Rick