If I understand your question correctly, I think what you are looking for is edit_post_link();
To use it just insert <?php edit_post_link(); ?> into your theme. This will output a edit link leading to the current page/posts editor.
Update after rewrite of question:
You can replace your link with the following to include the posts slug in the url.
<a href="http://blah.com/shop/<?php echo $post->post_name; ?>/edit">
You might want to look into also replacing the hardcoded link http://blah.com/shop/ with a more generic like home_url();.