this function checks whether the page is the order received page, and if so, checks whether the order contains the bundle product, and if so, outputs the tracking pixel on that page. Put this file in your themes function.php file

woocommerce_conditonal_product_purchase_tracking_code.php

/** Add tracking pixel if order contains product ID. Replace 11747 with your specific product ID */
add_action( 'woocommerce_thankyou', 'bundleTracking' );

function bundleTracking(){

	/* do nothing if we are not on the appropriate page */
	if( !is_wc_endpoint_url( 'order-received' ) || empty( $_GET['key'] ) ) {
		return;
	}

	$order_id = wc_get_order_id_by_order_key( $_GET['key'] );
	$order = wc_get_order( $order_id );

	foreach( $order->get_items() as $item ) {
		if( $item['product_id'] == 11747 ) {
			echo '<img src="https://twilightnight.com/p.ashx?a=504&e=518&f=img&t='.$order_id.'" width="1" height="1" border="0" />';
		}
	}
}

it should be noted of course that you''ll want to modify line 16 to include whatever your tracking pixel actually is.