Try this:
To create an actual button for your product pages ...
Go to includes/languages/english/button_names.php and add the following
Code:
define('BUTTON_IMAGE_WISHLIST', 'button_wishlist.gif');
define('BUTTON_WISHLIST_ALT', 'Add To Wishlist');
Now save that file to includes/languages/english/YOUR_CUSTOM_TEMPLATE_NAME/button_names.php
Create a button image that you'd like to include on your product page, save it as button_wishlist.gif to the includes/templates/YOURTEMPLATE/images/buttons/english folder.
On your product page add the following where you'd like the button to show up.
Code:
<?php
// (un): start wishlist link
echo '<a href="' . zen_href_link(UN_FILENAME_WISHLIST, zen_get_all_get_params(array('action', 'products_id')) . 'products_id='.(int)$_GET['products_id'].'&action=un_add_wishlist') . '">' . zen_image_button(BUTTON_IMAGE_WISHLIST, BUTTON_WISHLIST_ALT) ?> </a>
// (un): end wishlist link
?>
Hope that helps.
Matt