You need a golden gecko. I don't think I would put a bananna in a fish tank, but my gecko LOVES them, and she actually prefers them over-ripe. A Golden would easily take care of your left over bananas!
Although they do need mealworms and/or crickets a couple times a week in addition to the fruit. So if you don't mind a few bugs here and there, it's a great alternative and extremly rewarding, they are a blast to own.