The original Xbox 360 power supply is a very good match for the printrbot GO if you want to use a heated bed. The PSU supplies 203 watts at around 12 V and is also relatively portable (it's like a chunky laptop PSU).
Although you could splice the output wires into a common ATX connector, you could also keep the original plug and lift a connector off of a discarded Xbox motherboard (there are plenty of these on eBay) and wire that to the printrboard instead, giving you an easy and elegant way to unplug it.
This housing for the PSU connector creates a nice permanent mount for the connector in the side of the GO. Just cut a 25 mm x 27 mm (approx.) hole in the side panel of the GO and mount it using two of the existing panel screws and add two more for the top of the housing.
The SCAD file does have some parameters, but was not really designed to be tweaked, that's just how I put it together. Consequently, tweaking any parameters will doubtless require additional manual tweaking of other hard-coded dimensions to make everything fit right..