I was doing a search and thought this might be useful info to have. There is a place in Punta Cana for mobility rentals. They are located near the Punta Cana airport and will deliver and pick up to any resort for an extra 20 US. Not sure how far out they will deliver. If you give your phone number they will call anywhere to give info and answer questions.
http://www.handicaptravelersdr.com/price-list
http://www.handicaptravelersdr.com/price-list