Thomarillion have released a set of 18 different metal cogwheels.
Cool for all the young modelers who don’t have any broken Walkmans lying around 😛
Ooof, 22 Euros/$30 seems awfully expensive for what is offered.
For the more cost conscious consumer go to a clock/watch repair shop and see if they have any old, unwanted gears. I’ve had luck with this in the past.
There are companies out there that sell gears by the bag, but they are generally plain looking.
Edmund scientific’s sells them and radio control car web stores do too.
Hassle free miniatures has a really nice set of them under Basing & Bags /fiddly bits.