Amazon has the MJSI HYR270 HydroRight Drop-in Dual Flush Converter for $17
with free shipping on orders $25 or more. Otherwise shipping is $6. Converts your toilet into a water-saving two-button version with a quick flush for liquids and paper. Approximate savings of 15,000 gallons per year for a family of four. Easy installation, but will not fit all toilets, read product description for details.