I honestly doubt you'll find replacement parts for 2 reasons:
Most people don't bother repairing any appliances anymore because buying new is cheaper than paying for repairs.
Manufacturers don't want you to repair broken appliances because they only make money from sales of new appliances, not from sales of spare parts.
What you could do is:
Browse ebay or ...
I am pretty sure you can find replacements on Amazon or ebay with those specific dimensions. I'm sure they have the correct gears. There is a step by step guide to replacing the gears on this site- ifixit.com/guide/amazonbasics+B0050BPWBQ+Shredding+Gears+Replacement/60193