Many RV and RVers carry air compressors. If you don’t have one, I would suggest looking at purchasing one that will work with your RV tires. Part of the daily trip inspection should be checking and filling tires prior to getting on the road.
Some RV (mostly motor homes) will come with a compressor used to inflate the air bags that act like springs on the motor home. These will have a port on the compressor or in the basement area for an external air hose. This external air connection can be used to fill tires. Make sure you have a good tire pressure gauge and use it frequently when filling tires until you know how much air the compressor is putting out.
If you need a compressor you want to get something that will put out more than enough pressure for the job. My motor home tires need between 95 and 100 psi. I purchased an 100 psi compressor and it took forever to fill a tire. Gave it to my son and upgraded to 150 psi compressor. Much faster.
Compressors are basically of two types; 12 vdc or 120 vac. This is an area that cheaper is NOT better. A cheap compressor will not hold up and will only waste your time, money and maybe safety. I carry two air compressors, a 12 vdc in the trunk of the car and a 120 vac in the motor home. Since I have a generator, I can use it anywhere and any time.
If you are buying a rig with a built in air compressor, make sure to check the pressure and operations. If the air tank has a relief valve, pull it to make sure it works. Also open the drain plug to make sure there is no standing water from condisation in the tank. If there is any water in the tank and it comes out muddy or rusty, have the tank checked by a qualified technician. Rusty tanks can explode and damage the rig.