My best suggestion would be to find some paint (duplicolor for example) that is for plastic and delivers a polished metal look. There are lots to choose from, so find the one that most closely resembles the color and shade of the wheel. Then rough up the entire wheel (the plastic part) lightly with fine scotch bright, clean it with denatured alcohol, and shoot it with whatever paint you decide looks closest to original. As an alternative,you could try just touching up the wheel with a small brush if you find a paint that is very similar, or you could plastidip them, etc. good luck!