Double sided Mousedroid Side Panels for the Mousedroid Builders Club, based largely on TinyP's exhaustive references. Also see the two teeny tiny daughter boards that go with this.
You'll want two of these per mousedroid. They're best ordered with black soldermask (which is a little glossy, so you'll likely be painting over it anyway with something less glossy), 1mm thick (keeps them lighter), with 2oz copper (so the details remain visible after painting).