Earlier this week, the Duchess of Cambridge visited the Evelina Children's Hospital, as she became a patron with the Duke of Cambridge. For her visit, Middleton wore the dress trend that has swept fast-fashion stores this year—a polka-dot dress. Her spotted long-sleeve green midi, featuring pretty pearl button details on the bodice and a bow tie at the neck, is by her go-to high street brand, L.K.Bennett. At the time of this typing, the $645 dress was still in stock, but there are also lots of other amazing spotty dresses online. In particular, we love the similar style dress at Zara in black, which is $50. Keep scrolling to see the duchess's dress and shop our favorite similar versions.