Do you means omething like: http://jsfiddle.net/qxqP9/2/
What I have done is keep your cloning script, removed everything from the last td (the button) and put in a place holder for your new button.
I have also added a placeholder for you to add any JS you need to to the new button :)
var newButtonHTML = "NEW BUTTON"; // This should be button HTML
$(newButtonHTML).children("button").click(function(e) {
// type new button click code here if needed
});