You should just be able to use a "circuit pen" from most any electronics shop to do the repair. Typically, these have a conductive glue-like substance in them that you squeeze out/ trace along the lines needing repaired. They aren't expensive: $5-10 maybe?

I would go that route, though the stuff used to repair rear window defroster lines would no doubt work much the same magic, and might even be cheaper.

If neither of these do the trick, I have a spare Duo keyboard (NOT a Rev. F) that I could sell. It is unusable in its present form (spongy in the extreme), so is an ideal parts candidate.

PM if necessary.