You should be able to find the paint match from any autobody paint supply store. The paint used on wheels is essentually the same as the paint used to paint the body. It is just a matter of matching the color, and if necessary could be matched by computer.
An alternative is that Griot's Garage carries an aerosol can of silter wheel paint. It is probably more closely color matched to european cars but it may be more than close enough.
http://www.griotsgarage.com/index.jsp 
