Kanye West started wearing these when he came out with the "Stronger" music video. After that, they have blown up and everyone loves them. They are not made by a specific company as a brand so you can find them anywhere. HotTopic.com has them in a variety of colors to choose from starting at $9.99 (depending on your location).
Honestly, this trend is not going to last that long so don't stock up on them. Pretty soon some new eye accessory will become popular.