Making a little light panel run by a battery.....

I want to make a little deal for Mo's halloween costume. I envision it as a little panel with maybe two rows of lights; the whole thing being no bigger than 8x4 inches.

I'm thinking I could take a piece of cardboard, punch holes in it, run the lights through it (something small kind of like christmas light type things) and run a wire into a backpack that would hold the battery.

Ideally the lights would flash randomly.

In the best of all possible worlds, I could buy everything I need at radio shack.

In fantasy-land it could be assembled by a monkey because I'm not much better at this kind of stuff than a monkey would be.

Honestly, even something like a rope light that I could rig to run off a battery rather than electricity would be pretty cool.

Anybody?

Thanks a million!