Replace "Add to cart" by a link to contact page on specific product

You can try this. I think it works fine.

/*PUT THIS IN YOUR THEME FUNCTIONS FILE*/

/*STEP 1 - REMOVE ADD TO CART BUTTON ON PRODUCT ARCHIVE (SHOP) */

add_action('init','remove_loop_button'); 
function remove_loop_button(){
    remove_action( 'woocommerce_after_shop_loop_item', 'woocommerce_template_loop_add_to_cart', 10 ); 
}

/*STEP 2 -ADD NEW BUTTON THAT LINKS TO PRODUCT PAGE FOR EACH PRODUCT
*/

add_action('woocommerce_after_shop_loop_item','replace_add_to_cart'); 
function replace_add_to_cart() {
    $link = get_permalink(get_page_by_path('contact-us')); //change 'contact-us' to your contact page slug.
    echo do_shortcode('<br>[button link="' . esc_attr($link) . '"]Contact us[/button]'); 
}