add_filter( 'woocommerce_empty_price_html', function( $price, $product ) {
	if( ! is_product() ) { return $price; }
	return sprintf(
		'
			<form method="POST" action="">
				<input type="hidden" name="action" value="ccom_request_price" />
				<input type="hidden" name="product_id" value="%d" />
				<input type="email" name="billing_email" required="required"
					placeholder="email address" aria-label="Email Address" />
				<input type="submit" value="%s" />
			</form>
		',
		$product->get_id(),
		'Request Price'
	);
}, 10, 2 );
add_action( 'template_redirect', function() {
	if(
		empty( $_REQUEST['action'] )
		|| empty( $_REQUEST['billing_email'] )
		|| empty( $_REQUEST['product_id'] )
		|| $_REQUEST['action'] != 'ccom_request_price'
	) { return; }
	$headers = [
		sprintf( 'From: %s <%s>', get_bloginfo( 'name' ), get_bloginfo( 'admin_email' ) ),
		sprintf( 'Reply-To: Website Visitor <%s>', esc_attr( $_REQUEST['billing_email'] ) ),
	];
	$product = wc_get_product( intval( $_REQUEST['product_id'] ) );
	$message = sprintf( 'Product: %s', $product->get_title() );
	wp_mail( get_bloginfo( 'admin_email' ), 'Price Request', $message, $headers );
	wc_add_notice( 'Your request has been sent. Thank you.', 'success' );
} );