Did you try Shapshifter yet? It’s got to be the easiest way to create a container for 3D printing. Don’t think much of the License agreement though! http://shapeshifter.io/
That is pretty cool.
I downloaded an .obj file.
Oh and Shapeshifter people, if you’re listening, you need an option for 0 Thickness. i.e. A solid model rather than a shell for just outline printing.
Useful if you want to make a vase or pencil holder!