Get a specific size from wp_get_attachment_image_src

Thanks maverick, your solution works

<?php  $args = array(
            'post_parent'    => $post->ID,
            'post_type'      => 'attachment',
            'numberposts'    => 15, // -1, show all
            'post_status'    => 'any',
            'post_mime_type' => 'image',
            'orderby'        => 'menu_order',
            'order'           => 'ASC'
       );

$images = get_posts($args);
if($images) { ?>


<images>
    <?php foreach($images as $image) { ?>
    <image><![CDATA[<?php echo wp_get_attachment_image_src( $image->ID, 'listing_gallery_2x')[0]; ?>]]></image>
    <?php } ?>
</images>   
<?php } ?>