Many years ago I stopped at a Chandler AZ Discount Tire store to ask about MH tires. "Not in stock but we can have them tomorrow", "OK let's set up an appointment", "Ohh we don't install them but you can take them to the guy down the street".
Since that time I assume that most shops can add air to a tire. But even then with "I need 120 psi in these tires which are now warm at about 115F and they don't know what to do".
There are some shops experienced in RV tires but from my experience most can just talk the talk and fall down on the walk.