shelf milk is just pasturized at a much higher temperature than regular refrigerated milk thats why its called UHT (ultra high temperature). It's not TERRIBLE but there is a taste diff. for sure. Don't ask me how I know so much about milk...I guess I was just as skeptical as you at first. Wiki search on milk...anything to avoid studying
But to answer the OP, you would probably have to get your hands on some dry ice for shipping overnight, how you do THAT on this island, I haven't a clue.