power flush system

You will have to buy a new toilet as far as I know. Sloan makes a valve that uses water pressure and it works well. Available in Gerber, Kohler and Crane toilets and probably others. Gerber version is very quiet but get a tall one because it has a very high water level that bothers some people. Nice think is that sloan valve requires almost no maintenance and they can detect back pressure and instantly stop flushing if they sense a problem. Overflows almost impossible. I have 4 in my house. They are older Kohlers and relatively noisy. My parents have 2 Gerbers that are very quiet.

I believe you need to buy the whole thing and not upgrade an existing one. The internal passages are not likely interchangeable.