I don't know any cops who have lights in their POVs. Guys making traffic stops & such out here while off duty isn't done. Use a cell phone, call dispatch if they really need to be stopped.
I have, however, pretended to be an officer from another jurisdiction. Happened a few years ago at the police memorial in Cleveland after the tattoo on Saturday night. I was wearing an NYPD t-shirt and she was silly enough to believe the line of bull I fed her about working there. Never caught on, even with my real PD uniform hanging in plain sight in the hotel room.