For diagnostic work, you do not need to hook up the Tech 2 to a 12 volt source. It will pull the 12 volts that it needs from the OBDII jack on the truck which it plugs into to operate. If you want to do programming with the Tech 2, then you you should connect it to a 12 volt source, but that is an increasingly rare procedure with the Tech 2.
My Tech 2 came with it own box and all of the various connectors. The reality is that I ONLY use the Tech 2, the CANDI module, the cord that connects the Tech 2 to the CANDI module, the OBDII plug, and the cord that connects the CANDI module to the OBDII plug.