http://cl.ly/code/0O1Y1c2a0e2b
I've had two cut at RazorLabs. I tried clear and smoked 3mm acrylic. Smoked works best for me.
The switch that Adafruit use is available at Phenoptix in a range of colours and the panel mount DC socket, in black or white is available on eBay here.
To assemble the case you 11 M3 x 12mm bolts and 14 x M3 nuts. That's enough for the case and the Arduino.