If you're looking for a dither to use in applications or games, the ones offered in this Oculus blog post (meant for use in realtime to improve image quality in VR) may fit the bill: https://developer.oculus.com/blog/tech-note-shader-snippets-...

By varying the dither pattern each frame they are basically doing the equivalent of the hardware FRC in monitors to give you an extra fake 9th bit (for 8-bit rendering) of precision - as long as the framerate is high enough, the dithering becomes nearly invisible. Not that it's super visible to begin with. I'm personally using Dither17.