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 a local market platform for someone offering a used paper shredder of the same model. I suspect most people only use the paper slot so you may be able to scavange the gears from the used machine.
Or order these specific gears to be 3D printed or laser cut according to your specifications. There are several tools available online that can digitally design gears of the same dimensions as the ones you want to replace.
If you go for 3D print, the gears must be resin printed to be able to withstand force. The cheaper extrusion prints don't form strong enough bonds between layers and would probaly break at the first test run. Resin printers print a whole layer in one go and the layers adhere to one another very strongly. Make sure your digital gear is completely filled in the center (to form a strong solid body) or the printer may replace all that material with a grid pattern, which is sufficient for most applications but not what you want.
Laser cuts offer insane precision and a wide range of materials that can be cut, but I'm afraid you'd have to go for steel (more expensive) because acryllic sheets (cheaper) are known to be brittle, especially at sharp angles, and I doubt wood (cheapest) would do much better.