Global site search - want to replace avatar with featured image...

Greetings! So, I want to set up a multi-site install w. a Marketpress shopping cart. I need all of the products to be searchable network-wide.

After reviewing info on Global Site Search, it seems this allows searches across multi-sites, but only for blog posts. This is not a problem, as I can simply create new products as Blog Posts.

The search results are an issue, however, as I would like the results to display a featured image rather than an avatar. If this was a 'normal' search form, the changes for this would be simple. Global Site Search is not simple to edit. I am looking at global-site-search.php, line 309
$avatar_default = get_option('avatar_default');

And then on to line: 328 with
. get_avatar($post['post_author'], 32, $avatar_default) .

How do I translate: <?php the_post_thumbnail( $size, $attr ); ?> into this format?

Or is there a better plugin which would search all network content rather than simply searching blog posts?

Thanks much!