This is main mechanical part you will need to make the robot.
You can find this sort of gear in VCR. Search garage sale or ask familly and friends.
The DVD is already obsolete thank to the BluRay, imagine how obsolete is the VCR! :P
The gear in the picture is from a VCR.
If you are really lazy, you can buy it from therehttp://www.allelectronics.com/make-a-store/item/GR-5/SET-OF-5-GEARS-AND-BUSHINGS/-/1.html