Woocommerce Sold Individually - with individual as default

functions.php

/* 
 * Sell Products Individually in WooCommerce
 */

add_filter( 'woocommerce_is_sold_individually', 'cj_woocommerce_is_sold_individually', 10, 2 );

function cj_woocommerce_is_sold_individually( $value, $product ) {
	
	$isi = get_post_meta( $product->id, '_custom_sell_individually', TRUE );

	if ( $isi == 'individual' ) :
		$return = true;
	endif;

	return 	$return;
	
}

if ( is_admin() ) :

        add_action( 'woocommerce_product_options_dimensions', 'isi_write_panel');
        add_action( 'woocommerce_process_product_meta', 'isi_write_panel_save' );

        function isi_write_panel() {
            echo '<div class="options_group">';

            woocommerce_wp_select( array( 	'id' 		=> '_custom_sell_individually', 
											'label' 	=> __('Sell Individually?', 'woocommerce'), 
											'options' 	=> apply_filters('woocommerce_product_visibility_options', 
												array(
													'individual' 	=> __('Individual Only', 'woocommerce'),
													'multiple' 		=> __('Multiple purchases allowed', 'woocommerce')
												)), 
											'description' => __('Limit the product to one per order?', 'woocommerce') ) );

            echo '</div>';
        }

        function isi_write_panel_save( $post_id ) {
            $_custom_sell_individually = esc_attr($_POST['_custom_sell_individually']);
            update_post_meta($post_id, '_custom_sell_individually', $_custom_sell_individually);
        }	

endif;