As I have said many times before, it is a great opportunity for an entrepreneur to set up a bus or min-van service from Punta Cana to Cabarete, Sosua, Puerto Plata and return to coincide with this flight's arrival and departure at a reasonable cost. I am sure it will work well, imagine setting up a web page with booking and foreign CC paying option and you are good to go. Even 20 people out of this flight picked up and returned (good thing is you always get the returns too as they buy a return flight) and he/she will be making a "killing" - sorry bad wording for current DR propaganda.... ! lol
As far as I have checked, there is no easy way and I would not want to do that trip with luggage twice ! Now with family and kids, forget it.... But a direct, reliable service, many might consider it.