If you are thinking of a conversion to modify yours to the flexible membrane push flush I wouldn’t advise it. The membrane circuit boards are notoriously unreliable and expensive to replace. In addition Thetford sited electrics in the cassette locker and these were susceptible to corrosion. Some owners have modified the system to site a more conventional switch adjacent to the toilet. I’ve got an electric flush and given the choice I’d be more than willing to revert to the manual zero hassle version. As far as modifying it would be worth looking at Thetfords website where you can see the respective illustrated parts diagrams. The easiest modification might be to obtain the required assembly from a breakers yard.