To answer the basic question, I don't believe that the patches are available onboard. So, even if you saw the doctor, you would get something else.
I also want to echo what some others have said: pretty strong side effects. My wife tried them on a couple of cruises, and on the last one the dry mouth and other symptoms were so strong that she will not use them again. We take ginger tablets, and she will take Bonine (Meclizine).