Redirect to custom WooCommerce Thank You page based on product attribute id (variation id)

show_custom_woocommerce_thank_you_by_variation_id.php

<?php

add_action( 'woocommerce_thankyou', 'redirect_product_attribute_based', 1 ); 
function redirect_product_attribute_based( $order_id ) {
    $order = wc_get_order( $order_id );
    foreach( $order->get_items() as $item ) {
        // Add whatever variation id you want below here
        if ( isset( $item[ 'variation_id' ] ) && $item[ 'variation_id' ] == 446 ) {
            // change below to the URL that you want to send your customer to
            wp_redirect( 'http://yoururl.com/custom-thank-you/' );
        }
    }
}