Well, I have looked through chassis One and Two for 123's....and the 616 manual... and the only reference to manual clutches is in the section on cruise control... showing the switch on the clutch pedal which disengages it ...

All steel tubing that I know of used on brakes is of the double flare style... not easy to duplicate on short pieces and them fit well...

How about cleaning it up and putting a couple of layers of heat shrink tubing around it to perhaps just get you home.... ?
Is it in the supply region or the pressure region ?