Buy these Cancer Awareness "Break Through...Find the Cure!" Purple Static Window Clings.
The "Break Through... Find the Cure!" 6" static window cling can be placed on your car window, or any smooth surface.
Can mount both ways, behind the glass or on top of the glass, but "clingiest" side is the back side so it clings most strongly on top of a smooth surface. The broken glass look is an attention getter, and you get your point across. An alternative to a ribbon car magnet.