YES !! — We call them Z-Rings. They are available as Mountain Bike Z-Rings (made in various sizes), and as Cyclocross Z-Rings (also made in various sizes and mounting configurations). Check out the product pages for details.
Secondly, small rings from the shifting rings sets are often used in single front chainring applications like single speeds. They work, but we recommend looking at Z-Rings first.
WickWerks technology is ever expanding. First, the World’s Fastest Shifting Chainrings using Bridge Shift Technology; Now Z-Rings, with a technology we call “Narrow-Wide Enhanced”.
Oh, and Z-Rings are Made in the USA.