Its really easy to make. Around here we get these toothbrushes for free from the dentist office.
Boil the water. (Make sure the pot is big enough to hold the entire toothbrush laying down.)
Pull out the bristles of the toothbrush while you wait.
Drop the toothbrush into the boiling water and leave it in until its extremely flexible. (Do not leave it in too long, it will melt. And do not take it out too soon because it will break easily.)
take it out of the water and put it on a dish towel.
Bend carefully into the shape of a cuff. (This particular toothbrush met a sorry fate)
Put into the bowl full of cold water and leave it there to cool.
Once its cool take it out and rock it.