The easiest way would be to use the Product Search: link
Enter in your price max ($50), select review status - without reviews, and then select "for free assignment" and "EF sponsored." Lingerie items are now also allowed to have one assigned review per item.
It's not necessarily the best method since most items are allowed to have up to 3 assigned reviews, but the system can't filter for that. You would actually have to check the reviews for each item to determine that.