Show a link to checkout below the buy button for Sell Media

sell-media-below-buy-button.php

<?php
/**
 * Plugin Name: Sell Media Below Buy Button
 * Plugin URI: http://graphpaperpress.com/plugins/sell-media/
 * Description: An example below button code plugin for Sell Media.
 * Version: 1.0
 * Author: Graph Paper Press
 * Author URI: http://graphpaperpress.com
 * Author Email: support@graphpaperpress.com
 * Text Domain: sell_media
 * Domain Path: languages
 * License: GPL2
 *
 * Copyright 2015 GRAPH PAPER PRESS (email: support@graphpaperpress.com)
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License, version 2, as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License or license.txt for more details.
 *
 * @package SellMedia
 * @category Core
 * @author Thad Allender
 * @version 1.0
 */
 
function my_sell_media_below_buy_button( $post_id ) {
	
	$settings = sell_media_get_plugin_options();
	$checkout_page = $settings->checkout_page;
		
	echo '<a href="' . esc_url( get_permalink( $checkout_page ) . '">' . __( 'Check Out Now', 'sell_media' ) . '</a>';		
}
add_action( 'sell_media_below_buy_button', 'my_sell_media_below_buy_button', 10, 1 );