Simple,
Get two small DC motors from radio Shack,
and a small piece of wood, wire, one-two 9volt battery(s), and 9 volt battery snaps.
And some sort of glue or sticky tack if you don't want to ruin the Warthog toy.
Connect the motors to the wires and the wires to the battery snap. and put the tack on the motors axel.
then stick it to the warthog. i would explain much better, but i am down with the flu and have a massive migrane, so it makes it tough to make this all sound right. But i drew a really fast, no where near my real design skills (you should see my good stuff), diagram to illustrate what i mean.
It would work, and i would explain how to incorperate a switch but i don't feel to well.
This would be a small project and cost money, but to me, building the rig would be fun and you would have a permanent set up you could take on and off the warthog. so heres the diagram.
Feel free to Message me with questions or anything, i'll answer when i feel better. It's off to sleep now
EDIT:
Ooh!
I just had an idea.
Scratch using a peice of wood as the base for this rig. Get a Project box (from radioshack) and build the rig in it. A project box is a small black sealable box where you can contain your little electronic projects and such.
*Film effects Training kicks in*
and if you have a good video editing program like Adobe Premiere, you could do Keying effects.
Keying is the Blue or Green Screen effects that movie makers use to cancel out the backround or to film say, a person jumping up in the air, then adding it to the real backround.
All you would have to do, is paint the project box very blue or very green, and then use the keying effects in your program on the box so you can't see it in the backround, but you would have to take a still shot of your back round so you don't see a box shaped grey area where the box was keyed out.
The purpose of the still shot is to have a picture of the backround to be an underlay so the grey box area isn't there.
But if you don't have keying effects on your program, no worries they sell short project boxes that would be concealed behind the side of the warthog, assuming your are filming from the side.
Good luck
Hope this helped
It's really less complicated than it sounds, just contact me with questions about any of it. and i'll get back to you.
-Justin