Adwords remarketing - product_attribute

[Poulsgaard]

Hi Core experts ;-)

I'm trying to implement tags on my shop for use in Adwords, remarketing.
I have several products, that have variants (different colors) so I would like to track exactly which combination the customer is viewing, to be able to show exactly that combination later via Adwords.

I’ve added this to my product.tpl file:
 <script type="text/javascript">
   gtag('event', 'page_view', {
   ecomm_pagetype: 'product',

   ecomm_prodid: {$product->id}_{id_product_attribute},
   ecomm_totalvalue: {$productPrice},
   isSaleItem: false });

</script>

I would need to get the id_product_attribute that the customer is currently showing.

$product->id is already available, but id_product_attribute is not.
- So how do I get that value?