How to programatically get the product id of newly added product using the commerce form
Provided that your additional submit handler is invoked after default one (which by looking how you added it, is the case), you can access nid of the node created as follows:  

function my_module_redirect_handler(&amp;$form, &amp;$form_state) {
    $node_id = $form_state['values']['nid'];
}


Now that you have nid you should be able to do required processing.

Hope that helps.