That's a nice look. The fender is likely to be an aftermarket cafe fender. Some bike I had in the past had a rubber guide loop with a protrusion that mounted to a hole in the side of the fender near the rear where the cable went past. I think it was the stock setup. Unfortunately, I don't remember which bike it was, but you might look around at a bike show or at ad photos on ebay. There are dozens of aftermarket tail lights available, but I don't remember ever seeing one on a BS. Something other than stock might look good with that front fender and paint job.