repair and get back on. I had an 80's motobecane I liked that snapped going up a hill the same way, they put a plate on the derailleur where it remained for the next 30 yrs.

I'd spend the $$ small amount of 150 and see it as an upgrade, if you like the frame. for that matter, the frame fits, and is in good shape still, make the history continue. you can always buy another bike in a year--------used or new upgraded--------- and start a new history on it while keeping the orig in riding condition.