Additional custom button for specific single product page in WooCommerce

Based on additional add to cart button with fixed quantity in woocommerce single product pages answer code, here is the way to do it:

add_action( 'woocommerce_after_add_to_cart_button', 'additional_single_product_button', 20 );
function additional_single_product_button() {
    global $product;

    // Define your targeted product IDs in the array below 
    $targeted_product_ids = array( 37, 53 );

    if( in_array( $product->get_id(), $targeted_product_ids ) ) {
        
        $link = home_url('/contact-us/'); // <== Here set button link
        $name = esc_html ( "Contact Us", "woocommerce" ); // <== Here set button name 
        $class = 'button alt';
        $style = 'display: inline-block; margin-top: 12px;';
    
        // Output
        echo '<br><a rel="no-follow" href="'.$link.'" class="'.$class.'" style="'.$style.'">'.$name.'</a>';
    }
}

Code goes in function.php file of your active child theme (active theme). Tested and works.

Other related answers:

• Adding a custom button after add to cart button in single product pages
• Add a button after add to cart and redirect it to some custom link in WooCommerce
• Custom Button next to “ADD TO CART” button of WooCommerce based on Product Type

You can use some third party plugins that will provide features to add buttons on a single product page.

or you can add a button in a single product file using coding .. you can use a single product file in the child theme from the WooCommerce templates folder.

or you can also use hook to add button in shop loop like this :

add_action( 'woocommerce_after_shop_loop_item', 'new_add_to_cart_button' );
function new_add_to_cart_button() {
    // Your button code.
}