Another thought is most states have these "Police Officer" associations that you can join for a small donation. I think they use the money for things like college scholarships for kids of officers killed in the line of duty, things like that.
Anyways, you give 'em a donation, and they give you a real official-looking sticker to put on your rear window that shows you donated to the association. Of course people will put these on the rear window so if they get pulled over, Officer Dirty Harry notices the sticker and may let you off the hook with a warning.
The ricers in question may also notice this sticker and think "Uh oh, off-duty cop" and back the hell off for fear of off-duty cop noticing plate number and store that in the memory bank for "things to do" between guarding the Krispy Creme and gassing up the Crown Vic.
You could also consider other tactfully applied decals like from the NRA and a parking permit from the local mental hospital, right next to each other.

Gilly