I need this "thing" that goes on the driver's seat and allows a handicapped person to sit on it, then rotate it (using their body) to position their feet on the pedals.

I don’t know what it’s called or where to buy it. I remember that some model cars COME with seats like this, i.e., you open the car door, sit down with your feet outside the door, then it rotates to make it easier to bring your feet inside the car.