Believe it or not, I actually ran into a guy who works at a company that makes these electronic reflectors. They come in a multitude of varieties and can be custom made to spec. The most interesting ones include the one with a little battery in it with a solar cell that trickle charges during the day, and a photo sensor to turn on at night and light up. There is one with a "fog" sensor with two metal things sticking out the side about 1mm. When it gets foggy they start blinking or whatever. And there are ones that are run on plain old batteries and can function for 6 years straight. Some of them are meant to be stuck permanantly, some are deployed with rubber bottoms during hazard situations. They're pretty cool. I can probably get one from them for $11 or so. They're probably a bit cheaper in bulk, but still not as cheap as plain old plastic of course.

Calvin