magento2 get custom product attribute on order success page

Question

I have a magento 2.2.5 based website and i need to get a custom product attribute on my order success page for each product. The custom attribute is called site_owned_buy any suggestions how to get it on the below code for each product I loop through

<?php
      $ga_data = [];

      foreach ($order->getAllVisibleItems() as $item) {
          $ga_item = array(
              'name' => $item->getName(), 
              'sku' => $item->getSku(),
              'qty' => $item->getQtyordered(),
              'price' => $item->getPrice()
          );

          array_push($ga_data, $ga_item);
      }

      $subtotal = $order->getSubtotal();
      $order_id = $block->getOrderId();
      $gtotal = $order->getGrandTotal();
      $address = $order->getBillingAddress()->getData();
      $city = $address['city'];
      $state = $address['region'];
      $country = $address['country_id'];
      $shippingVal = is_null($order->getShippingAmount()) ? 0 : $order->getShippingAmount();
      $taxAmount=$order->getTaxAmount();

    ?>



  <script type="text/javascript">

   dataLayer.push({
        'event': 'purchase',
        'ecommerce': {
          'purchase': {
            'actionField': {
               'id': '<?php echo $order_id; ?>',                      // Transaction ID. Required for purchases and refunds.
               'revenue': '<?php echo $gtotal;?>',            // Total transaction value (incl. tax and shipping)
               'tax':'<?php echo $taxAmount;?>',                     // Total tax value
               'shipping': '<?php echo $shippingVal;?>',          // Total shipping value
               'coupon': ''                           // Optional field and may be set to empty string

        },
        'products': [ 
            <?php foreach ($ga_data as $item) 
                  { 
            ?>        
              {
                'name': '<?php echo $item['name']; ?>',                      // Name or ID is required
                'id': '<?php echo $item['sku']; ?>',                          // Name or ID is required
                'price': '<?php echo $item['price']; ?>',                    // Insert product price
                'brand': '',                    // Insert product brand
                'category': '',              // Insert product category
                'variant': '',                // Insert product variant (e.g. red, black, etc.)
                'quantity': '<?php echo $item['qty']; ?>',                      // Insert product quantity
                'coupon': '',                          // Optional field and may be set to empty string
                'site': ''
            },
  <?php 
    } 
?> 
           ]
    }
}
});

Answer 1

Modified your code below. you need to load product from ID to get Attribute value:

<?php
  $ga_data = [];

  $objectManager = \Magento\Framework\App\ObjectManager::getInstance();


  foreach ($order->getAllVisibleItems() as $item) {


    $productId = $item->getProductId();
    $product = $objectManager->create('Magento\Catalog\Model\Product')->load($productId);

    $ga_item = array(
          'name' => $item->getName(), 
          'sku' => $item->getSku(),
          'qty' => $item->getQtyordered(),
          'price' => $item->getPrice(),
          'site_owned_buy'=> $product->getData('site_owned_buy')
      );

      array_push($ga_data, $ga_item);
  }

?>