You could create an options page, or add a field to an options page, that lets the admin choose a post from your custom post type and then use the examples in from the links. Instead of setting a specific page as in the code you would get the value from your custom option field and use that value to set the post. The to eliminate confusion you could add some custom CSS to the regular admin page to hide the standard WP selection. Like I said, I dug around in WP code for a while and there’s no way that I can find that will allow you to alter that drop down.
