These are 3/4 inch brake cups which you should be able to find at an auto parts store. I doubt you will be able to get the outer seals so you will have to re use the old ones. If they are leaking, and I suspect they are, then you might want to change them as the cylinders are likely pitted and will continue to leak. Brake fluid on your brake shoes is a bad thing.....
Dan Caron's
SL Barn
benzbarn@ebtech.net
slbarn.mbz.org
1 877 661 6061