Christian Zimpel

This Plugin makes the Thumbnails clickable with any URL you want and open it in a new tab.
There will be new Field called “External URL” on the Product data. Just fill in any URL i.e. Affiliate URLs you want.

Thumbnail Link for Wooc

This Plugin makes the Thumbnails clickable with any URL you want. There is an Extra URL Field within the Product.

jmarreros

This Plugin allows to use an external image as Featured Image, this can be especially useful if you house your images in another location.
This Plugin is compatible with Nelio External Featured Image Metadata, so you can reuse your data in case you want to uninstall Nelio Plugin.

External URL Featured Image

It is what I was looking for: simplicity.

$external_image = get_post_meta( $post->ID, '_dcms_eufi_img', true );

Works well for me

Use an external url image as Featured Image for your posts, pages, and other kind of post types.

Thumbnail Link for Wooc vs External URL Featured Image