I had to replace a battery in one of my Estimote beacons, and the only way to do that is by slicing the case open. It's a shame to lose such a cool enclosure, so I printed a new one to replace it. Roughly the same footprint, and a snug fit for the board. Everything snaps together - you may need to break it to get it open again.
It doesn't have the snazzy faceted faces on it, but I did add a small hole to loop some string through to hang it from something.
Made with Tinkercad - play with the file here.
Printed with PLA and a 70º heated bed to keep things nice and flat. 5% infill, three shells.