This may not be 100% original, but a good option. Manual disc master Rock Auto shows some 1.125" masters for front disc too. Front disc master No mention of power or manual in specs.
You know, back when these cars were new, it was SOP to rebuild master cylinders. I don't even know if rebuild kits are still available, but the FSM explains how to do it. You basically dismantle it, hone it out, and rebuild with new piston seals. You use alcohol to lube and clean everything.
Well looky here: 1967 master rebuild kit