This is great fun and a nice progression from our Brush Robots!
Small motors are cheap at any electrical store as are the battery casings. I got mine from Maplins. Adding a plastic bottle top off centre causes the vibration. These can be easily and painlessly stopped with a finger while in motion. Here is a little video of one in action.
We’ve tried taping ours to margarine tub lids, paper cups, sponges and so on, observing each object glide across the floor. I was inspired to add the coloured pens to make three and four legged bots by this post from Science Buddies! I had to make adjustments to make it safe and accessible to 1-3 year olds. Thank You Science Buddies! It was great fun!
Battery casing with wires
Plastic cup or lunch box
Science for toddlers!