Or you can use a normal servo motor with a wire connected to the horn going through a hole, to translate the rotation from say 0 degrees to 90 degrees to up/down. Here is a site that talks about servos: Make: Projects.
In terms of where to go, I suspect the best place is places that caters to robot building and radio controlled cars/airplanes. Given it is the first week of October, you probably don't want to go to Chinese internet shops if you want it for this Halloween. If you live in the USA, two US distributors I would suggest are:
Besides robot/rc shops, you might want to check out your local toy store and Radio Shacks for the various science toys, etc. You might also browse the Halloween stores that might have various things that could be modified. These places are probably better visited in person, than trying to order online.