Parts I purchased:
1) 60RPM Speed Reducer Rectangle Shape N20# Magnetic Mini Geared Motor 6V DC (Amazon, http://www.amazon.com/gp/product/B00AUCGJX0/ref=oh_aui_detailpage_o08_s01?ie=UTF8&psc=1).
2) Coaxial Power Jack (Radio Shack part number 274-1583).
3) 3.0 Vdc Power Supply (Radio Shack part number 273-315 with the "N" style plug 273-345, you get one free with the power supply).
4) 3 "marbles" (8mm ball bearings purchased at a local Ace hardware store, also available on Amazon).
5) Large rubber sticky feet (available at hardware and dollar stores).
Print all pieces as shown in "Assembly.skp". Carefully remove the hold down pads on "Base.stl".
Test fit and trim, file, sand, etc. all parts as necessary for smooth movement of moving surfaces, and tight fit for non moving surfaces. Depending on the colors you chose and your printer settings, more or less trimming, filing and/or sanding will be required.
Assemble as per "Assembly.skp".
Lubricate all contacting moving surfaces with light machine oil.
Wiring is pretty straight forward and simple, however you'll need minimal soldering skills and soldering equipment. Basically, solder a 3" red wire between the gear motor "plus" terminal and the coaxial power jack "Center" terminal, then solder a 3" black wire between the gear motor "minus" terminal and the coaxial power jack "Shield" terminal.
Comment if questions.