Spray painting my helmet?

I want to spray paint my lacrosse helmet. I've looked into it, and it seems that auto paint that comes in a spray can will work best, but that's pretty expensive. What other types of spray paints would work well on the plastic surface? It needs to be something that can take a lot of contact (obviously being a helmet) and not chip off. I want a matte color, and does that mean that both the actual color and finish would have to be matte? If you have any advice, please let me know.