You've just punched up the hardest to get parts especially when it's a 20 inch machine of which there are so few around and no one would wreck a 20 inch machine, rather they would move heaven and earth to rebuild one and have it going again.
I might be able to help you with a chain case.
Cheers, BB.
I live a 24 Hour lifestyle, but every now and again I seem to fall asleep, well at least that's what my wife tells me.