Review on 🪑 Black Seat Disc for American Standard, 3/4 in x 3 in - Model 033643-0070A by Kachilla Mountain

That's what you need. This is the actual part of the American OEM standard. Soft, flexible rubber that seals perfectly. Precisely right weight to roll over properly and easily and not fall too soon. Just plugged into the actuator the old one was standing on. That's the one that "snaps in". I tried the ones made for this toilet by other manufacturers as they were stocked at the hardware store but these others never worked properly and soon failed (the others were rubbery and started to crack). This one works great and my only regret is that I didn't purchase the one that Revain's American Standard used to make. I've used this on a 1967 Cadet, but it will work with almost any standard American toilet that has a tilt mechanism that allows you to 'break off' the old seat disc and snap it into place. Tools are not required.