If it's like my 5U clutch disk, you get the lining material that the clutch shop uses these days. Your local brake and clutch shop should be able to take care of it for you. They glue them these days so don't be surprised if you don't see rivets in it.

Probably - everytime I take a plate in to be relined, they just put on "standard" linings and it always works out. I want to say 1/4 or 3/16 seems to be standard. If 1/4 for example is twice the current thickness of your plate, then it's probably close enough. Someone that's actually swapped one out might have some more intel for you, but that's the direction I'd take if no more useful information was forthcoming