Forklift brakes - it's a wonder I could stop at all!

If the cylinders are not too badly rusted/ pitted in the bores, I would try and find an old school parts outfit and see if you can get cups. The boots don't "look" too special if you find some that size.

Shoes, look for an outfit that can still rivet lining. I've relined some shoes and winch bands, from early 70-s up into the mid 80's. Yeh, I know, that is getting harder to find. Actually if you can find some similar lining, you could hand rivet lining yourself. You basically need a vise, a tool to back the rivet head, and a "setting" tool. You'll need some cheap clamps to hold the lining until you get some rivets in.