Summary

My three year old asked for a magic wand for his wizard costume.
I used a straw from a bubble tea as the handle, because it fits AAA batteries really well.

Instructions

The handle is a bubble tea straw. Cut the point off and it should be about 25cm long.
Print one of each STL.
If you want, add your child's initial to the star top, with the included 123D source.
Note that the printed M3 bolts will not have a proper thread (unless you have an amazing printer!), but the lumpy result makes a great locking bolt that fits snugly.
Source: http://www.thingiverse.com/thing:193647
For the AAA contact in the handle base, I just used a blob of solder. Then bend a little U into the cable to fit it snugly into the base part.
For the top contact, I used the spring from an old pen.
Push it all together, lock it in place with the bolts and you're done!

Magic Wand