What I'd do is look for a car with the metallic finish I want, make a note of the make and model (and guess the year), then go to Pep Boys or similar place and pick up some primer, sandpaper (including really, really fine grit) and the appropriate "touch-up" spray paint for that car.
Sometimes the can itself will include the make/model it's designed for, or you can do some research beforehand (there's probably an online forum for that make of car) and find out the paint code, or find out what standard touch-up color is close enough.