Don't know about the new networked (Command Link) digital gauges, but the older digital ones had a separate wire for lighting. I connected mine to the circuit powering the side marker lights, as if I needed the gauges, I'd be underway, and I often leave the white anchor light on while diving.
I'm unable to locate any kind of wiring diagram/schematic at the moment, but I'll keep looking.
Can you describe your gauges? Round, square; sort of a description of the connectors supplied?