Create node link in views header and open in popup
I think you are looking for hook_menu_local_tasks_alter to create the 'add node' link.  As for the popup... perhaps you are speaking of the administrative overlay?  If that is the case and you have the overlay enabled, the 'add node' task should open in the overlay automatically.

You're probably looking for something like this (taken from this post):

function YOURMODULENAME_menu_local_tasks_alter(&amp;$data, $router_item, $root_path) {
  switch($root_path){
    case 'path_of_your_page' : // for example 'page/view/news'
      $item = menu_get_item('node/add');
      if ($item['access']) {
        $data['actions']['output'][] = array(
          '#theme' =&gt; 'menu_local_action',
          '#link' =&gt; $item,
        );
      }
    break;
  }
}