Call your local medical supply company (the one that sells wheelchairs, canes, etc.). Sometimes they have scooters or electric wheelchairs to rent. Don't know if they are cheaper than what the show gets, but worth the call.
One other thought...if you need a scooter for medical reasons, why not have your doc order one? Medicare and most insurance companies cover them, so you will own one outright and not have to worry about renting, etc. Just a thought...