Replace your old toilet innards with this new dual-flush water saver system for siphon toilets in about 15 minutes—the hard part is getting the old stuff out! This is a third-generation dual flush that just has one handle: down for heavy, up for light, and is fully adjustable for bowl height, and both flush strengths. Also comes in 3-inch model. Completely replaces those annoying flappers and chains! New system just slides right in to the 2-inch flush hole.
I got this at Home Depot.