For my first build I decided to go with a Yamaha break switch. It appears to be well made. Making the bracket to hold it was easy. Took some scrap 1" angle iron and cut two 
s. The first one 1" long, which I drilled a mounting hole through it for a 5m stainless bolt. The second one cut to 2" with a 1/2" hole drilled to hold the switch. It's important to get the sizes right and drill the holes before welding. Makes for much easier assembly. Next I welded the two s to form a box. Make sure the orientation is correct before welding. Then sanding or sandblasting and painting. Before mounting the switch I removed the spring and reversed it to hold a pulley. Mounting the cable to the spring itself not a good idea, it kinks it and creates a break point. Next I mounted the pulley and turned the spring end over and around so the pulley cant come off. Next I made a cable clamp. Using 1/2" scrap solid steel rod I drilled one hole big enough to pass the width of two cables. Then I cut it off at about 1/2". I then drilled and tapped for 6m stainless steel bolt perpendicular to the first hole. As you can see it came out very nice, all that's needed for it to be finished is to cut the cable and crimp a cable end on it. The electrical connections will be done after I fabricate my electronics box.
http://i.imgur.com/25O8cVU.jpg
I did test it's operation. The switch has an internal spring so there is back tension, which means no erroneous contacts caused by vibration. I set it so I don't even have to apply the brakes to activate it, just pulling the dual brake lever about 1/4" will turn my brake lights on.
Hope this helps out. Having a break light is very important in my area, would highly recommend it where ever you ride.
Have fun and stay tuned to the AssembleThis channel!
s. The first one 1" long, which I drilled a mounting hole through it for a 5m stainless bolt. The second one cut to 2" with a 1/2" hole drilled to hold the switch. It's important to get the sizes right and drill the holes before welding. Makes for much easier assembly. Next I welded the two s to form a box. Make sure the orientation is correct before welding. Then sanding or sandblasting and painting. Before mounting the switch I removed the spring and reversed it to hold a pulley. Mounting the cable to the spring itself not a good idea, it kinks it and creates a break point. Next I mounted the pulley and turned the spring end over and around so the pulley cant come off. Next I made a cable clamp. Using 1/2" scrap solid steel rod I drilled one hole big enough to pass the width of two cables. Then I cut it off at about 1/2". I then drilled and tapped for 6m stainless steel bolt perpendicular to the first hole. As you can see it came out very nice, all that's needed for it to be finished is to cut the cable and crimp a cable end on it. The electrical connections will be done after I fabricate my electronics box.http://i.imgur.com/25O8cVU.jpg
I did test it's operation. The switch has an internal spring so there is back tension, which means no erroneous contacts caused by vibration. I set it so I don't even have to apply the brakes to activate it, just pulling the dual brake lever about 1/4" will turn my brake lights on.
Hope this helps out. Having a break light is very important in my area, would highly recommend it where ever you ride.
Have fun and stay tuned to the AssembleThis channel!
If you haven't a dual-pull or integrated shifters, the switched levers ebikes use to activate regen can also be used to switch any LED brake light instead as it's your basic momentary on, two wire switch. This two-tone aluminum set is commonly found on ebay & amazon for as little as $8-10, ebike retailers usually offer the same for a few bucks more; 
