I want a brighter brake light

The first thing you can do is go to the Bulb Comparison Chart and find which one will work best for you.

Elsewhere in the FAQ you will find a writeup on adding bulbs into the empty pods next to your brake light. This adds significantly to your safety out on the road.

One product you can buy is from Aerostich, the Stopper LED Brake Light. This is a row of LED lights that attaches to the top or bottom of your license plate. It acts like the middle brake light on a cage and will give you more visibility.