Here's a screw-together black acrylic box specially designed for the Useless Box.
This is just an acrylic box with screws for assembly. There aren't any electronic bits - unless you already have the interior components, this is an even more Useless Machine, with exciting "does absolutely nothing except be a box" action. The full kit can be found here.
This is just the box, cut out of black acrylic, and ready to assemble together with 20 sets of 4-40 nuts & bolts.
Be prepared to spend a few minutes peeling the protective paper off the acrylic (it helps to loosen the glue with a hair dryer).
Want to cut your own? Get the layouts on the resource page!