+1 SunTour MountTech. I use one on a bike that's set up 28-46-50 and it works fine, just fine. Reasonably attractive as well.

-1 to Simplex Presige, that thing has a hard time with a 4-tooth shift. Almost completely useless, and the narrow cage means you basically have to trim it every time you shift. Not hard to see why Simplex is no longer with us.