I have a Campbell Hausfeld 12-volt tire inflator that has kicked around in the back of my car for years. I’ve lost count of the number of times I’ve re-inflated a tire with a slow leak, and then gone on my way. The brand isn’t nearly as important as the fact that it runs off your car battery; it has a tire pressure gauge built in, and it has a work light.
Small 12-volt compressors like this run from between 15 to 30 bucks new, and will do a fine job of re-inflating tires or rubber rafts or volleyballs. Most compressors come with attachments that will do all of these things. In my case, we often travel on industrial roads that lead to the local dump, so we tend to pick up more than our share of nails and screws. My little compressor has lasted through several cars and many tires.