Hobby shops that sell radio control equipment often have boxes
of miscellaneous gears in hand. You might find a good fit.
An old desktop copier or laser printer might also have what
you need. Don't substitute metal for plastic casually. The
soft plastic gears might be a safety feature, shearing before
the cutter blades damage something or the motor overloads
and burns.

indago wrote:
My daughter purchased a document shredder. The name is Shredder Essentials
Model SES - C810 Serial #B07130500876

After some usage, it stopped working. I opened the casing and found that
there were two nylon gears that had stripped. I contacted Shredder
Essentials on their WebSite and asked for their service manual, and told
them what had happened. That was a couple of months ago, and I haven't
heard from them at all.

I would like to replace the two gears with metal ones. Failing that, I
could just replace the nylon gears with new ones. I have gone through
Google and have had no luck finding a repair kit for this shredder. Maybe
the gear train is a common one and is used in other shredders. Does anyone
here have any info on this?