I've always wanted one, so I decided to design one for paper. Its still a work in Progress on the mesh side, but its getting closer. It may take some time before release, as I'll be building a vanilla beta version before texturing it. It looks complex, and it will have lots and lots of parts (I wanted a fairly high detail one), but most of the parts will be variations of the simple box, so all it will require to make is patience. Here is a WIP mesh screenie.