Help! I broke my master cylinder push rod.

I have a 1974 Duster with the factory power front disc brake setup. I was replacing the master cylinder today, and when I went to adjust the length of the MC pushrod the adjustment nut on the end of the rod broke off (see photos). Any ideas as to what to do? Obviously, my car is undriveable right now and I need a fix. What do you think? Can I repair the old one? Do I need a new one? Does anyone repro these? Any and all ideas welcome. Thanks!

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