I like this custom one off I got years ago:
That looks like the work of Gary Spradley, although I believe he stopped making them years ago. I have a custom grab bar light that was custom made that I bought off of a member here years back, not as bright as the one above but is noticeable in sunlight so it works for me. I have since made a better fender mounted tail/ brake light.
^ I agree, I followed a lot of guys at Thunder that had the CBR mod and during the day they were Very hard to see.
An LED light in place of the rear reflector helps a lot with visibility.
I actually decided on a 60 LED Cateye tail light just because I was Not happy with the CBR light's daytime visibility.
Mine is Very visible even during the day.