I would get a propeller from a toy "hotwheel" airplane, of sorts. There will probably not be any flying model propeller small enough for your needs. You could, however, go to a smaller, static model airplane and possibly find something that would work. You could always rig it up so as to use a smaller rubberband motor--something that you could spin backwards against the rubberband, and then let it go, so spin freely during the scene. Of course, you'd have to cut, and re-energize the motor after a while, but you might get off pretty cheap this way. The only other option would be some small motor like a watch motor or something similar that would run off of very small batteries. How big is the nose? There are a number of very small motors out there, it depends upon how big the false nose is.

Please post a picture of this contraption once it is built, I've very curious about it!