A DC supply will normally have a zero volt connection for the return current, i.e. you need two terminals to complete the DC supply of course. It is correct to call one of the terminals 0V and the other is -ve or +ve with respect to this terminal.
If you want you can think of this as a...
You could try Tru-lon they are based in Royston in the UK and have experience of manufacturing Microwave Ceramic PCBs.
See this link ...
http://www.tru-lon.co.uk/capabilities/materials.htm
