Hydroboost for 89 c60

[rkn463]

Pulled the hydroboost unit from my 89 c60 and it has been leaking both inside the cab and outside. Seal kits and rebuilt units are readily available for 1/2-1 ton trucks but this thing is a monster and my initial searches are coming up with little of nothing. Does anyone know a company that specializes in brake parts for medium duty trucks? I had info once for a place in Atlanta but I can't remember the name, seems like it started with an A. Here are some pictures I took of the markings, unfortunately I did not get a pic of the complete unit.

Thanks in advance,
-Richard