Phoenix area 12V install off ignition

So I'm gonna lay out a platform of sorts in my Access Cab to kinda like below, and
set my Dometic 35 in there. But I need another 12v cuz my current 12v is used for
my brake-controller on the teardrop.





This is the Dometic DC Hardware kit that I wanna put in the backseat area or if it fits
in the slot just under the dash. I want to wire it to the ignition so it only draws when
the engine is running and the Dometic is plugged in.

Who in Metro Phoenix would you trust to do this - I got no skills when it comes to
tools and mix that up with anything electrical and you got a disaster waiting.

Thanks

 

Or.... you could get one of these:

$10 ELECTOP Cigarette Lighter Socket Outlet Splitter, 12V USB Outlet USB Charger 12 Volt Socket Power Outlet with LED, Waterproof Power Socket Panel Adapter DIY Kit Dual USB Ports for Car Boat Marine RV

https://www.amazon.com/gp/product/B077MC3L3B?ie=UTF8

Do some research and then install it in the back of your armrest.







Here is a video for reference: https://www.youtube.com/watch?v=SrljRuG3coI