The ones I installed used a belt from the factory wheel over to the add on wheel and a master/slave cylinder to actuate the brakes and a bicycle brake cable to operate the accelerator. I first got involved with the hardware through a customer who needed a vehicle to teach the disabled how to drive with hand controls and the instructor needed to be able to take full control from the passenger seat. After installing that first unit the supplier referred postal carriers, etc to me. I made a quick search just now and saw similar units
but I don’t recall the source for those I installed. The equipment I dealt with was extremely well made and although several holes were drilled into the floor if the unit was removed there would be no obvious indication of the removal.