I would look at either replacing the gear entirely by either buying a new one, or finding a local 3D printer in your area who can replicate it for you. Is it metal, nylon, plastic...?
Lots of times when the feed dogs aren't pushing fabric, it's because they're completely impacted with lint and need to be cleaned out. Don't use canned air unless there's a clear path for the dust, lint, and thread to go through the machine and out the other side.