<div id="containeur">
    <input type="button" value="Test" id="test_bouton" />
</div>

<script type="text/javascript">

    function clic_bouton() { alert('Bouton cliqué'); }
    var bouton = document.getElementById('test_bouton');
    var containeur = document.getElementById('containeur');

    bouton.onclick = clic_bouton;
    var clone = bouton.cloneNode(true);
    clone.id = 'Test2';
    clone.value = 'Test2';

    containeur.appendChild(clone);

</script>