well sorry I missed that part
best suggestion then will be pull the one's you have and go to a good farm ag tractor store with them (one that has been imn business a LONG time too, as they will have most experience with things and possibly find you some)
and ask to see if they can match them up for you!
MY guess is, it might be a outdated part and this is why they don't want to carry them, they most likely had things custom made for there implement and then changed things to use more universal parts, so not to have to pay overhead on keeping parts for JUST THERE implement
so, it might be a issue finding new one's
you can try contacting some tractor/implement salvage yards and see if they have any , but I think you might be in for a hard find here!, and most likely why previous owner sold it, as they couldn;t find new one's!
best of luck!