How to make a template for a specific post of a custom post type?

As Pages are a special built in Posttype, they get an own template hierarchy. Other “normal” post types and custom post types can only be templated by “single-$posttype.php”. You can however hook into the single_template filter and make wordpress redirect to your template file:

function get_custom_post_type_template($single_template) {
     global $post;

     if ($post->post_type == 'account') {
          $located = locate_template( 'account-'.$post->post_name.'.php' );
          if ( !empty( $located ) ) {
                  return $located;
          }
     }
     return $single_template;
}
add_filter( 'single_template', 'get_custom_post_type_template' );

I didn’t test this, but it should work ^^

Happy Coding,

Kuchenundkakao