Why buy the spur gears for you Automated Build Platform when you can print them yourself.

Spec Alert!
Unit : Inch
Diametral Pitch :32
Teeth 18
Bore Size 0.1250"
Pressure Angle 20°
Face Width 0.188"
Pitch Dia. 0.5630"
Hub Dia. 0.3438"

This spur gear match perfectly on the shaft of the original 20mm DC motor:
http://www.kysanelectronics.com/Products/Detail.php?recordID=1231
The shaft for the conveyor belt needs to be grinded down like the shaft of the DC motor.
They pressfit on the shafts, so no need for any screws.

My spur gears where printet with 0.3mm nozzle and no cleaning afterwards except removing the raft.