I made one when I was bored, long ago when my grandmother still ran her store and my uncle still ran his immigration law firm on the third floor, and when I was obsessed with knot theory, out of computer paper, tape, and a lot of hard pencil. I still use it, and it cost me next to nothing.

EDIT: If requested (however unlikely) I will happily deliver a picture, and either a push or a bouillon cube (your choice). EDIT THE SECOND: it was requested! http://imgur.com/a/kxanI