Remove "insert into button" in media uploader for custom post types

Looking for a way to remove the insert into post button in the media uploader for a specific custom post type. I can do it when the post type is in the url but when you edit a post, the post type isn’t in the url.

ex.
post.php?post=27&action=edit

I tried $post, $typenow and $current_screen but the only one that works anywhere so far is $_REQUEST[‘post_type’]. Not sure if part of it is using just add_action('admin_head', 'remove_insert_button_13247')

In any case, how do I detect the post type when editing a post, custom or other?

function remove_insert_button_13247() {
    echo '<style type="text/css">
        .media-frame a.button-primary {display:none;}
    </style>';
}
function get_current_post_type_13247() {
global $post, $typenow, $current_screen;
 if( $post && $post->post_type )
$post_type = $post->post_type;
 elseif( $typenow )
$post_type = $typenow;
elseif( $current_screen && $current_screen->post_type )
 $post_type = $current_screen->post_type;
elseif( $_REQUEST['post_type'] )
 $post_type = sanitize_key( $_REQUEST['post_type'] );
else
$post_type = '';
 return $post_type;
}
if ( get_current_post_type_13247() == 'listing') {
	add_action('admin_head', 'remove_insert_button_13247');
}