My robot lawn mower (a Robomow rx20u) was moving erratically, so I took apart the wheel assembly and found that one of the reduction gears has several broken teeth (in the picture, look at the right-hand side of the smaller gear. The diameter of the larger gear is 37 mm).
I've found a replacement for the whole motor and reduction gearbox, but its price is about 80 USD. I think that the broken piece costs about 1/100th of that.
Does it make sense to shop around until I find the right gear, or is it a hopeless task and I'd better buy the whole assembly?
What sites / shops do you suggest to consult if I want to buy just the gear? (I think that 3D-printing it is out of question.)