Since that's a short answer, here's some examples (without making any sort of recommendation)
Do consider the colour before wearing - In my country Blue (police) and Green (medical service private transport) are reserved colours that must not feature on a road vehicle. Also Red must not face forward and White must not face rear (unless reversing)
I have used something similar to the blue one and it works as described, but they're not bright enough to see with. 2x CR2016 batteries don't last long, and CR2032 are only marginally better.
You could also get the same effect using electroluminescent wire and stitching it to a velcro strap.
The easiest solution is to use a small red rear light and clip it to the back of your traffic-side foot or pedal. Some risk of it falling off though.