At Boden, search for "WH650" to find the Boden Women's Jessica Dress in Navy (pictured) or Party Pink for $29.60 plus $10 for shipping. That's $118 off list and the lowest total price we could find. It's available in sizes 2R to 18L.
Ralph Lauren offers its Denim & Supply Ralph Lauren Women's Star-Print Tank Dress in French Navy Ground for $25 plus $5 for shipping (select economy at checkout). That's the lowest total price we could find for the dress in any style by $17, although we saw it for $5 less two weeks ago. It's available in sizes S and L.