'rewrite' => array(
            'slug' => 'catalog/%product-cat%',
            'with_front' => false
        ),

add_filter('post_type_link', 'product_type_permalink', 10, 4);

//session_product is the custom field in the session CPT that references a product
if (!empty(get_post_meta( $id, 'session_product', true ))) {

  //gets the product id
  $id_product = get_post_meta( $id, 'session_product', true );

  //gets the product title
  $title_product = get_the_title($id_product);

  //gets the permalink
  $permalink_product = get_post_permalink($post = $id_product, $leavename = false);

}

catalog/%product-cat%/a-custom-post