I too have come across this problem. I was working at a shop where I could air up my own tires but it can make it a lot of work just to do that. Sometimes it's not my vehicle I need to put air in the tires, some times it's my significant others car. During this winter I just had it!! We live by a truck stop, and 2 gas stations all a mile or two apart.
When it came to airing up my tires this winter I drove a mile to one gas station, same air machine is STILL out of order for weeks, went across the street and same story it's been weeks, went to the truck stop and it's also out of order. Myself growing up with a 8 gallon air compressor this was tough for me. Not being able to air up my own tires??
I thought about a 12 volt air pump but they burn out and also they are loud and take forever. My friend sold me a CH 2 gallon air compressor for 45 $. It fits my need because I'm still working to purchase a heated garage. I also tend to use an air inflation gauge to check my tire pressure while I air up my tires.
I'm not sure what you do daily but it sounds like you run different vehicles and not just one. With a semi truck, and an air line attached to the red glad hand you can fill your own tires all day long with the trucks air compressor and air tanks.
Honestly driving to the tire store may be the best bet for now. I know exactly what you are going through. I fear it is quite a hassle before a large trip and you want to air up your own tires. You could carry around a 5 gallon air compressor in your vehicle and power it with a large power inverter. Either way it just cost so much money to have something portable and reliable