I would personally take that 123 whatever the hell it is and recycle it. Install a fluid master, and a normal stand tube and flapper, and never look back. Unfortunately, the new standtube will require removal and re-installation of the tank. Buy a new tank to bowl washer and bolt kit while you are there, and a new SS Braided toilet supply. Take the old tank to bowl doughnut with you so you can match it up.
Happy Flushes to you.
" A lot of men build things, and a lot of things fall down "