HTTP_SERVER.'index.php?route=product/product&product_id=' . $product['product_id']

Href karşısına bunu yapıştırın eskisini silin.

$data['products'][] = array(
                    'order_product_id' => $product['order_product_id'],
                    'product_id' => $product['product_id'],
                    'name'              => $product['name'],
                    'model'             => $product['model'],
                    'option'            => $option_data,
                    'quantity'         => $product['quantity'],
                    'price'             => $this->currency->format($product['price'] + ($this->config->get('config_tax') ? $product['tax'] : 0), $order_info['currency_code'], $order_info['currency_value']),
                    'total'             => $this->currency->format($product['total'] + ($this->config->get('config_tax') ? ($product['tax'] * $product['quantity']) : 0), $order_info['currency_code'], $order_info['currency_value']),
                    'href'              => HTTP_SERVER.'index.php?route=product/product&product_id=' . $product['product_id']
                );


Bu şekilde yaptım ama siteadi.com/admin/index.php?route=product/product&product_id=65 şeklinde çıktı