I'm actually thinking about getting some of that flourescent yellow 3M Engineer-Grade reflective tape, and putting a few stripes on my helmet. That way, it will still look high-vis in the day, but will also be reflective at night.
Either that, or I'll put a few bits of electroluminescent wire on the thing, and then my helmet will be lit up too...
I keep saying I'm going to do this, but I keep procrastinating too.