The problem of simply replacing the broken part is that all treadle bases are not the same size. I've tried a couple times to replace the broken piece on my 9W-7 treadle and both replacement pieces were a different size. They looked the same, but off buy a bit.
Luckily the second one is close enough to be used.
If I could find a welder that would do the job for a price I could afford I'd have it repaired .
Joe