I have one like that. I made the top gasket...
I sent the body off to be sleeved at Apple Hydraulics..but you could sure try to rebuild it as is if it's not too pitted.....
My cap was different....I was able to find a new one online...
I bought the cap from:
Brake Products Inc
PO Box 23547
Chagrin Falls, Ohio, 44023..
They may have other parts....