My new bus is based on the sprinter. Behind the steering wheel, on the dash is a little 'cubby' with a handy USB socket. My sprinter has two batteries, one for starting & the other for everything else - mind you, it needs plenty of juice to run a tail- lift plus sliding door & electric step!
On the plus side, as soon as the key fob is pressed to unlock the vehicle, my cam starts recording & the dual batt system doesn't interfere with the supply when I turn the engine on.
I have my Mobius mounted behind the mirror on the bottom of the rain sensor/lane departure etc, cowl.
When I press the fob to lock the vehicle, the usb socket continues to power the cam for another minute or so.
Happy days.
The lead runs across the back of the cubby, under the dash. Held in place with lashings of blu-tack. It then comes out of the cubby and disappears behind the window pillar trim and across the top of the screen. A practically invisible install.
Good luck with your install