When motoring the States, I was shocked to disciover I need to pay to pump air in my tires... and that air pumps don't have a pressure gauge!

In Europe, air is free and pumps have gauges! (or... should I drive to the fuel pump with a funnel and my own length of hose?)

Anyway... more than quarters, a small +12V plug and a miniature air pump are a safe choice.
Some double up as a flashlight and LD starter.

If the small electric pump is too bulky, a HD bicycle pump is just as good for pressures up to 30-35psi.

Also... H4 lamps for the front light, spare tail/stop and indicator lights, and some red transparent tape to fix the taillight.
Last... we all know inner tubes have the tendency to leak a little bit of air so a possible option is to deflate your tires completely and refill them with FIX-A-FLAT (tube type) and ride with "unflattable mousse".
I did this to my old Guzzi and she maintained the proper pressure for years! (until I sold her to a loving new owner)

Else, who knows, these guys might manufacture motorcycle tubes as well !!!