WDW resorts do not have wheelchairs for guest use other than emergencies — and even then I understand a CM will push (like to your room) and keep the chair. Not something you can borrow.
Just a couple hours is probably going to be hard to find. I don’t know if any of the vendors rent for short-term use like that. Sometimes local civic organizations have devices that can be borrowed - have you looked into something like that from home to bring with you?
I would ask the front desk if you are already there. We were able to "borrow" one at Coronado for a few hours 2 summers ago. You never know.