Jandre,
Welcome to the H31 braking system dude, most advanced braking system at the time but, those things are harsh, its actually power steering fluid that runs the hydro booster, and thats what your leaking
I have a place here in JHB that reconned both my hydro unit as well as my master for like R900 including strip and refit. I actually have a spare hydro unit here, but its seal is leaking as well
Your unit I am sure is leaking on the triangle, where the 3 bolts come together to mate the booster and the master unit. Any decent hydraulics shop can sort that out for you, that seal should actually be quite easy to replace.
Phone around to brake specialists with hydraulic testing equipment, dont take it to the mech that works out his garage, he will not be able to fix it, but any decent brake specialist should be able to sort it, if not, strip it out, send it up to JHb, and David will get both units reconned.
New is out of the question (the master is like 12k from agents, let alone the booster), second hand you will battle to find, as you have to find a unit that is still in a car and has fluid in it, else the seals will be gone..
Do not let anybody tell you that those units cannot be reconned, cause its not true, and be careful with the pressure inside the hydro unit, it needs to be spot on, else you will have reduced braking, or if the pressure is too strong, you will keep on popping seals on the master, been there done that.....