Here's my latest reproduction - Omega Supreme walking cogs. They work just like the originals, I even devised a way to print the spring that goes inside it. I used a set in my OS and they work perfectly. I know someone else casted these in the past, but as I far as I know I'm the only one currently producing them.
If you're going to use it as a sig picture, it might work to put two cogs in the image, seeing as how you're selling them per pair.