Are you talking about to connect it to your PC and perform updates? If so, you can get the serial-to-USB cable and power supply from Radio Shack. Or you can search for the DiabloSport U7778 adapter kit and order it online.
The specs for the power supply are in the Predator update instructions...
NOTE: These cables can also be purchased at Radio Shack, or any electronics supply store:
-USB to Serial cable OR a straight 9-pin Serial/Serial cable
-12 v 1 amp power cable 2.5 x 5.5 mm jack, center pin positive.