Simply filing or grinding down the dogs might not be as straightforward as it seems. You need to ensure that the modified dogs still engage properly and provide enough grip to move the mower, especially on inclines or in thick grass.
The problem with trying to grind down the dogs is that the gripping teeth are short and if you decrease the diameter of the dog there would be no teeth left to grip the tyres.( To attempt this you would need to machine them down in a Lathe then machine the teeth into the dogs )
It would probably be easier to make a sulky for the mower and you could just use a couple old bike wheels or whatever you can find.
Grinding down the drive dogs is unlikely to be a successful or safe solution. Building or buying a sulky is a much better and more practical approach to controlling the mower's speed and making it easier to operate.
I guess another option is to find a few old mower shops and see if they have old stock of the smaller drive dogs.
The larger dog drives are made for the sulky see pic below from owners manual.
