Logo size on loop

I want to show a logo on the loop (product catalog), but by default the size for the loop is set to “thumbnail” and there’s no option to change that. On single product page it shows perfect.

The only way I found was to edit the code in the next file:
perfect-woocommerce-brands/classes/class-perfect-woocommerce-brands.php

on line: 184

$attachment_html = wp_get_attachment_image( $attachment_id, ‘thumbnail’ );

I changed ‘thumbnail’ to ‘full’ and it worked!

But if you update the plugin I’m going to lose the change I made.

Is there any other option to change that?

Thanks a lot!