Hi Mel-
The tail uses a mini cell-phone/ pager motor- they are very tiny! You can find them lots of places on the web- one to try is:
www.allelectronics.com
They offer many different types of motors, switches, and all the material you need.
try to find one without the weight on the end- they are very easy to mangle trying to get those off. I found another web store but the link escapes me at the moment.
-Len