Kid Sized Ghostbusters Proton Pack! (under $20!)

So last year, I was a Ghostbuster for Halloween, using the incredibly awesome proton pack I built.  There were a couple of problems with the costume, so I decided to fix them and upgrade the costume for this year's Halloween.

While I was sitting around rewiring, touching up, and adding arduino control to my pack, my daughter told me she wanted to be my "Ghostbuster Assistant."  I kind of hemmed and hawed and told her I didn't think I had the time or money to build one this year, but the idea simmered in the back of my brain for a while and later on that week I realized that not only did I have enough time to do it, but I had almost everything I needed already on hand! 

Total cost for this project: $15.88 (under $20!)

Most of the materials were scraps of cardboard and plywood, various doodads and gizmos I had in my shop, and lots of stuff rescued from the recycling bin.  The electronics, tape, and hot glue I already had.  All I had to buy was one tube of E-6000 epoxy (4.99) and three cans of super cheap flat black spray paint (.97/each).  Also, I had to pick up an old backpack from value village (2.99) for the the straps.  Oh, and a khaki jacket from goodwill (4.99).

Here's a brief description of the controls:

Okay, as I've mentioned before, user Honus has made a very nice and much more professional 'ible on how to make a Ghostbusters Proton Pack.  I used his instructable for reference, but the main difference was in the materials.  Also, I didn't bother to stay exactly true to the movie props, which I'm sure for "serious" fans is a no-no.  I wanted the pack to LOOK like a Proton Pack, not actually BE a Proton Pack (or to have to run around finding all of the exact parts).  The dimensions I used were based off of several prints available at this website, and I stayed as true to the plans as I could, but I didn't limit myself to them.  I also made my rough measurements about 2/3 smaller, so it would be more kid sized.

I used mainly cardboard, tape, hot glue, and epoxy to make the packs.  Here is a (probably incomplete) list of the materials you should have lying around to make a kid sized (or a full sized) proton pack:

1/4" plywood
Lots of cardboard - big boxes and a variety of smaller boxes is helpful
Duct, masking, and electrical tape
2" thick styrofoam (I used this because I had it, but cardboard would work too)
Flat black spray paint (Home Depot sells cheap cans for .97/each)
Hot glue
Epoxy (I like E-6000)
Strong magnets
Wires
Split plastic conduit material
Plexiglass
Probably about 10-15 feet of light gauge speaker wire
LED's, perfboard, a 555 timer, switches, buttons, capacitors, resistors, flashy kids toys from the dollar store
1/2" and 3/4" PVC (about 8 feet of each)
Eye screws
An IDE cable from an old computer
Some colored wire
Miscellaneous bottle caps, screws, bolts, zerks, tubes, pill bottles, and any other sorts of things that might look nice once they've been spray painted