Rebuilding Matco Brake cylinder

[Jbuzz]

My right brake cylinder started leaking bad enough that I had effectively no right brake. I ordered a rebuild kit from Matco and with it came everything I needed except for some adhesive to glue the buna plug to the shaft. Matco calls it Black Max, or anything compatible with the brake fluid. I cant find it anywhere and everyone I talk to has no idea what I'm talking about. The cylinder is a mc-1 model. Does anyone know where to get it or any alternatives that would be compatible.
Thanks for any help