They are bolt on seats only, not a full toilet style bidet. You can see a bunch of them here on amazon. tushy ones seem to be pretty popular over on the place that will not be named. They are low on frills (like no heated water typically).

Personally, I splurged for a Kohler with all the bells and whistles (definitely wasn’t $30). OMG it’s hands down the greatest thing I have ever bought. Heated seat, air dry, heated water, amongst other things.