Gearbox options for Fisher Price

[MrForbes]

We made one using the first stage gear from an older FP gearbox, which has the 3/8" hex hole in the gear. The high precision plate that locates the motor relative to the gear was made using a cheap vernier caliper from the physics class to measure the sizes of the gears and the spacing, and lay it out, and a small drill press and Forstner bit to drill the 7/8" holes. You can't see the hex part of the shaft, but it's there, between the bearings. The hex shaft has to be turned to fit into the bearings, alternately if you could find some bearings with 3/8" hex holes in them?

http://www.andymark.com/product-p/am-0439.htm