Hello Mary Lynn,
Disney does rent out Electric Convenience Vehicles (ECV) for your use throughout the parks, but they are available on a first come, first serve basis. I've found some local companies for you to try. I have not personally used these though.
Apria Health Care (407)291-2229
Care Medical Equipment (407)856-2273
Turner Drugs (407)828-8125
Walker Mobility (407)518-6000
I've also attached Disney's webpage regarding
wheelchair rentals. It's very informative so please take a look.
I hope this information helps you. Have a magical vacation!