Damn you, lol. Beat me to it. My reply *would* have been: "I built it in the desert from a bunch of scraps..."A box of scraps.
where did you get the arc reactor from?
But seriously. Light system was very slightly modified from a Superman light up kryptonite toy, and the reactor frame shape was cut from a set of photoetch pieces from a 1/35 scale WWII half-track PE upgrade set.
I drilled the chest hole, backed it with sanded clear plastic to diffuse the light, and drilled a hole on the rear to access the battery.
It's pretty basic. The switch is on Tony's back and you can feel it under his shirt