I remember long ago someone mentioned in this thread that you could buy the Sphero R2D2 droid for like $30 - so I did a few months ago. I'm just now getting around to designing the framework to mount this on top of my pin as a poor man's topper
What you see here is just the framework - testing for fit and stability. Once I add lighting and make it look like it's in the back of an X-Wing, I'll have paid less than $100 and can take it out so the kids can still play with it