Scott Bolinger

GTINs (Global Trade Item Numbers) including UPC, EAN, and ISBN are globally recognized unique identifiers for products.
They are required to list your product on Google and Amazon, this plugin allows you to add your GTIN and display it on your product page.
Supports:
<ul>
<li>Simple products</li>
<li>Variable products</li>
<li>Composite products</li>
<li>Product bundles</li>
</ul>
Features:
<ul>
<li>Add GTIN for main product</li>
<li>Add unique GTINs for product variations</li>
<li>Option to display GTIN on the single product page</li>
<li>Change GTIN to any other text</li>
<li>Add GTIN to structured product data</li>
<li>Works with product feeds like Google Shopping and more (requires a feed plugin)</li>
</ul>

WooCommerce UPC, EAN, and ISBN

Awesome plugin with great code

Add GTIN codes like UPC, EAN, and ISBN to your WooCommerce products.

Joan Rodas

Sirvelia

Generate Amazon universal links to redirect users to the Amazon site of their country.
This plugin uses http://www.geoplugin.net to geolocate the user IP in order to redirect to the appropriate Amazon store.

ASIN Smart Links

Generate Amazon universal links to redirect users to the Amazon site of their country.

WooCommerce UPC, EAN, and ISBN vs ASIN Smart Links