This is a pdf of all the pieces for the companion cube
I made. If you print it off at the default size, you should end up with a cube about 3" square, which is the size I made mine.
Remember that the companion cube belongs to Valve, so you can't use this pattern for commercial purposes. It is just for your own enjoyment!
If you would like the tutorial that goes with this pattern, you can find it on my blog: Part I
& Part II