I think you have to find like a 1964 model to not have power brakes
Just get some more leverage/travel. Raise the pedal pivot up and lengthen the arm (or pound the floor lower and lengthen the arm). My golf never really had power brakes, no sweat.
edit: I suppose you could also change where the plunger connects with the pedal slightly, for more leverage, and maybe increase the pedal travel by grinding on something.