I've always wanted to have a brakelight in the topbox: there's an option to buy one specially designed for this box. But I think this set would have cost me more than € 30, and also the set has normal light bulbs in them and I don't want to increase the electrical power consuption.
So, when I bought the 2 white Bikevis bullets for the front of my bike (www.bikevis.com/), I also bought 2 red ones.
I removed the plastic lens from the lid of the topbox:
Then drilled two small holes in the plastic bit that was designed to take the original brake light and stuck 2 red LED bullets in position. The power wire is routed through the box & comes out through a small hole in the bottom.
The right photo shows what it looks like when the LEDs are burning. I still have to make the electrical connection to the motorbike.
NTV650 (1996) owner from 2004 to 2014. Current bike: Suzuki DL650 ABS (V-strom / 2012)