I don’t like relying solely on a reflector to make myself visible from the back so I got this:

(Clicking on the item will bring you to the item I bought)
It has 5 very visible LEDs that can either be all fully lit or make patterns that reminds me of KITT in Knight Rider)…
It takes two AA batteries and seems to last a long time on those…
At the same time I bought another one for my brother who rides my previous bike.
By the way, while we are on the subject of KITT, my (Garmin) GPS which I intend to use with my bicycle once I get the proper holder has its/his voice… I got the personalized version which calls me by my name…
Stay tuned…