Typical Espresso Beans?

Good for you for experimenting with your new machine! I think that the Columbian dark roast is a reasonably good substitute for espresso beans, but I would also try French roast and even Mocha Java, if they have it. There is no actual "espresso" bean, this just refers to the dark roast they put on it. But some grocery stores do carry espresso roast beans. Have you thought of asking the person that stocks this section whether he could add this to the collection of beans they offer?