Are you talking a street legal kit or a supermotard kit? If you talking street legal then i'm pretty sure that's impossible. If you are talking supermotard then i have no idea. I would think anything that works with the newer 450s would probably work with yours. As far as i know they just change the wheels, tires and suspension.
NOTHING is impossible! I understand in Colorado getting a plate on a bike is not real difficult either. You might be looking for a Baja Designs kit perhaps?
I didn't think it would be very easy to get a two stroke plated unless it was a moped, in which case you don't need plates. At least not around here. But maybe i'm wrong. Let me know if it works for you cuz that would be pretty cool.
I have seen more plated 2 strokes in Colorado than any place else I've visited. 4 strokes are just more popular these days so everyone thinks getting a plate on a 2 stroke is impossible. I also am pretty sure that AJ has plated at least 1 CR500AF.