We didn't find renting diving equipment in Bavaro. But when you go for a trip with diving, then equipment is included in price.
On the beach Bibijagua there you can rent a boat with captain and equipment for 75USD per person (min. 4 persons) for half an hour of diving.
If you have special licence for caves, then you can try caves here in the DOminican REpublic. Price is about 400USD per person. In the price is equipment, food, drink, quide included.
The Dominican Republic is paradise for all divers. In case you don't have your licence yet, you can undertake divng course. It is for everybody from 10 years. You begin in the pool and then you will go tot the sea. YOu will get know all details about safety and in the end you get your PADI licence.