I believe the PMC8 has reverse polarity protection. As the PMC8 uses the "standard" 5.5 x 2.1mm center positive plug, you'll find options readily available.
Note to Jerry: I'd like to see ES include at least a DC power cable as that's what the competition is doing and these mounts will be judged against competing products in the same price class.
That being said, a Celestron power cable will work just fine. I made my own using Anderson Power Poles. I also made my own battery box for less than $100 including the deep cycle battery. If you don't need something that big, there are plenty of 12 volt battery options.
I'll dig out a parts list when I get home.