another option I have done before and works well, "House of color" has a product called adhero--adhesion promoter, you can clean the lenses with acetone, then spray adhesion promoter, then spray them with purple candy coat, and a coat of urethane clear and they hold up very well. Just like paint on your car. I have done the same on kustom painting Harley v-rod's candy painting over the aluminum panels.
Just another way at doing it all the materials are not cheap, so if you are going to do it might as well line up a hand full of them and do them all at once.