This is a cheap solution for anybody wishing to add more light to the back of their touring bike.
I chose to wire mine as an additional brake light but it could also be used as a running light. Readily available at AutoZone parts stores for $17.95, it's a quick and easy installation that really makes a difference.
I've seen a number of different mounting methods used but I simply purchased a couple of handlebar clips at my local Home Depot store, drilled a hole in each one, screwed them to the light and then the entire assembly just clips onto the rear chrome support bar under the trunk. It's been there for almost 2 years now with no problems at all. Total cost will be about $20.00 including the clips.