NAPA has a straight in tire gauge too that will fit thru the hole in the wheel pants. I took the straight inflator and put it on my Harbor Freight inflator setup with the gauge built-in. It works great for checking and adjusting pressure now.
The above from Amazon works well. flexible inflator and gauge.
Line up the valve stem and wheelpants hole then paint a vertical stripe on the inside of the tire, so you can see it when pushing/pulling on the tow bar.
I bought a flexible 6" valve extension, and keep it in the glove box. When I'm traveling, I can toss in a tire pump or my Ryobi inflator and not have to worry about finding a compressor.
I don't remember the place I got the extension from. It looks VERY similar to this one, but with heat shrink over the female fitting end so you can poke it through a hole in the wheel pant and screw it on from the other end. And of course it cost 3-4x as much.