Need correct CSS language to hide external link option button in marketpress

Hello, I am using marketpress along with tt-marketpress frontend and on the create product page (see screen shot)there is a post box for users to add an external link. I would like to hide this using css if possible on the wp-style page of the tt-marketpress frontend. I've hidden a few other things this way. For example, I hid the add category toggle by using this code:
.tt_mp_fe #product_category-add-toggle {display:none;visibility:hidden;}
Does anyone know the proper css language I would need to hide this external link box?