I have bolted to my rack a Planet Bike Rack Blinky 5 and two (2) Sunlite TL-L225 lights. They can be found on Amazon very easily, and they do come with a rack mount, though the one with the Sunlite is a little different, but it works.

Here are the lights mounted on my rack:



And here's what I look like from the back at night:



As I said, the Sunlite rack mount is a little different, but works just as well. It allows me to rotate the light in to either a vertical or horizontal stance.