Surprisingly this switch's PSU converts AC to only 5V. On idle and boot, it only consumes 15W. Of course with SPFs, and more connections, this will probably require more power. To this end, I chose a 50W 12-24v to 5V converter (others are available, but i thought a wide range was a good idea).
The connection from the AC PSU to the Netgear motherboard is 6 pins. 3 are 5V+, and 3 are 5V -. Why 3 connectors are needed for each i have no idea, as they are all connected.
There is also enough space inside the case to contain the converter, and a switch to choose either AC of DC power sources.
I used the cable management bolt hole and a washer to secure the new DC converter to the case. It's not pretty, but it fits and doesn't touch anything that could be dangerous. I added a switch so that the DC or AC source could be selected, although I would wait until it is off before switching sources, just in case!