my friend just made hers out of a clear plastic cube, like a baseball display box or maybe an old x-mas ornament box. something like that LOL
then she put wrapping tissue paper on the sides, crumpled for a marbling light effect. then she had some blue, submersible LED lights ([link]) that she put inside the box. i think a 12-pack at michael's was about $12 after the sale it was on.
overall it's a pretty easy project, good luck if you decide to have a go on your own