DIN rail enclosure for a Arduino + Ethernet shield
You could design and build your own with laser cut panels. This guy's arduino and shield look the same as yours.

http://www.iheartrobotics.com/search/label/A%20Case

http://www.iheartrobotics.com/2010/03/case-for-arduino-laser-cutouts.html?utm_source=feedburner&amp;utm_medium=feed&amp;utm_campaign=Feed%3A+IHeartRobotics+%28I+Heart+Robotics%29

http://www.shapeways.com/model/85671/arduino_case.html