I have a Road Pilot Micro-Go speed camera unit. It came with a normal cigarette lighter plug on the power lead. I purchased a lead with has a cigarette type 12v socket on one end and bare wires on the other end. I connected a ring connector to the earth (black) wire and a spade terminal to the red wire. I then used my multi-meter to find a spare ignition controlled spade in the fuse box in the right-hand end of the of the dashboard and connected the ring on the earth lead to one on the fixing bolts in dash and hey presto, the Micro-Go comes on with the ignition and goes off when I tirn the ignition off. All the wires and the socket are wrapped in foam and tucked behind the dash. I have the Micro-Go at the lower right-hand end of the screen and the wire just tucks in the joint between the dash and the car body. Works a treat.
I think I bought the 12v lead off ebay for £3.25. If you decide to go down this route let me know and I will check to see which spade connection in the fuse box I used.