I had an onboard air setup on my Jeep—and it seemed like something similar for the truck would be even handier when we are traveling fulltime.  Should have pulled it off the Jeep before selling…but since I didn’t I just ordered one of these 12v units as they have been well-used by the off-road crowd.  They have some faults but the fixes are well-documented in discussion forum threads like this.

The truck has a nice open spot under the hood on the passenger side that I’m hoping the unit will fit into - I’ll hardmount it, and run an air line to the rear bumper for a connection point that’s mid-way between the truck and trailer.

Hopefully this setup will save us the hassle of trying to maneuver the truck and trailer around to check tire pressures at a gas station.