im not to sure the place we are getting one for my mom from they drop it off at your hotel and it beaks down pretty small and can go in a mini van PM me if you want the info on it
I rent off site with walkers mobility and they have waiting on me when I get off the ME at resort and I have until I leave to return home. I load and unload on to the buses as we do not drive down there any more nor rent a car. so much easier to take the disney transportation. there are other off site ECV rentals as well.
There isn't any of the car rental companies that rent vehicles with a lift on the back. There are 2 reasons for this. One is that the lift has to be hard wired to the vehicle. The other is that the ECV has to be fitted for that lift. They can't just put one on there and it will work.
If you want to rent a car to haul the scooter specially, then you would have to rent a wheelchair van, but these are way more expensive than just a regular van.
If it was me, I would just rent a ECV from someone like Apple, who rents the travel size scooters that break down to fit in a trunk. Just make sure that wherever you rent the ECV from knows that you need it to come apart to fit in a rental vehicle.