You should be able to accomplish this via ACF (Advanced Custom Fields). When you create the custom field you assign the
post_type to a WooCommerce product.
Then in the products loop you just make use of ACF's
get_field() to fetch it. Maybe you have to query the ID of each product and then insert it in ACF's function like this:
get_field('my_text', 123); (id = 123).