Do they exist???

 

that actually light up??? maybe with a watch battery.

 

Think about it, how will they know when to turn on, or when to blink. Unless you have like bitium said, a watch battery in them. The funny part will be that they will stay on forever, or as long as the battery would.

 

They exist, but just not a real side market. Instead it looks like a reflector kind of thing.

 

That's only for the trailers.