Parma's Fasklolor is supposed to be a 'universal' paint, for Lexan R/C car bodies and plastic models, so you could give that a try. I'm told it is just the craft paint Createx, with or without a flex agent to keep it from flaking off the flexibile Lexan bodies, depending on whom you believe.
http://www.parmapse.com/fas1.html
It is very thick, and will dry flat, do you'll have to thin it and clear coat it. It's also an acrylic, but they SAY that spray paints will work over it (They recommend backing them up with regular R/C spray paints, which are lacquer-based, in order to seal them from the fuel used in gas cars).