I want to suggest another option to try fixing the gear, 2 part epoxy. Someone gave to me a DialnSew ZZ machine, it was quite stuck up top, and while trying to loosen things up I broke one of the cast metal pieces which controls the ZZ function. I used a single use Loc Tite product which cost $2.75. I used brake cleaner to degrease the part first and also used some thin metal wire to reinforce the spots where I used the epoxy. After allowing it to cure and removing some of the excess, I put the machine back together yesterday and ran it, and the part didn't break...yet. I have to get it all together and oiled up before thread testing, we'll see.
The epoxy is oil resistant, which was a plus, and a cheap fix without which I'd have a parts machine because the broken part is practically speaking irreplaceable.