The 37-year-old royal donned a silk Figue Frederica floral printed ruffle frock, which retails for about R20000, on an official visit to the University of the South Pacific campus in Suva.
Within hours of the tour images being shared online, the gown was no longer available to buy.
Meghan teamed the pom pom-adored dress with a $7,300 (R105 000) Shaun Leane serpent bracelet and her favourite Castañer Carina espadrille wedges that she previously wore on Bondi Beach last Friday to mark the Suva university's 50th anniversary.
This isn't the first time the former 'Suits' actress - who was known as Meghan Markle before getting married in May - has had websites crashing with fans eager to get their hands on the coveted pieces she's been pictured in, which has now been dubbed 'The Meghan effect'.
Meghan has attracted plenty of attention for her simple-but-chic looks on the tour of her 16-day tour of Australia, New Zealand, Tonga and Fiji and even wore a piece from her pal Serena Williams' fashion line.
On the second day of her royal tour when she went to Dubbo, Meghan wore a grey blazer from the tennis icon's collection.
The royal opted to wear a double-button style blazer with patch pockets and a red-and-blue windowpane pattern.
Serena, 37, was thrilled that her friend sported her blazer - which has now sold out - and took to Instagram to reveal her joy, sharing a picture of the duke and duchess holding hands and smiling.
She wrote: "The face you make when you and Duchess of Sussex Meghan have matching @serena blazers." (sic)