There are additives available that allow paint to 'flex' with the plastic surface - or, at least, there used to be many moons ago. It's mixed with the paint and thinners and normally used on spoilers/wheel-arches, etc. The downside was, it could sometimes affect the finish if not used carefully. But paint technology is always advancing, so there might be something available today in a can, though I'm guessing it will be expensive.
Painting plastic is half the battle. Getting it to stay on is something else. Good luck.
I've a feeling I'm not in Kansas anymore.