New Zealand designer Karen Walker has also experienced an influx of online orders after Meghan has been spotted wearing her earrings, sunglasses and most recently her trench coat while braving the windy Wellington weather.
Karen Walker communications manager Jiali Yang said the trench the Duchess wore yesterday was already in production and in a few hours the web store had sold out of the pre-orders available.
"75 per cent of these orders will be shipped to the US, and the rest will go to the UK, Australia and within NZ."
Designer Karen Walker said this trench coat was one of the brand's most beloved silhouettes.
"It first appeared, in classic tan trench coating, in one of our shows at London Fashion Week in 2004. Since then we've refreshed and revisited it many times and it continues to be a favourite.
"Her Royal Highness looks very chic and we're delighted that she's chosen to wear Karen Walker once again," Walker said.
Meghan wore the brand's black Northern Lights sunglasses and a pair of 9ct gold stud earrings on two separate royal engagements during her official visit to Australia with her husband Prince Harry.
In the 19 hours since the spotting of the sunglasses, the Karen Walker website sold more than seven times the number of units it sold the month previously - most orders came from overseas.
The tailored coat with double-breasted front will sell for $975 when it becomes available in mid-November.
On another official outing to Bondi just days earlier the duchess wore Karen Walker's temptation earrings priced at $399.
A spokesperson for Karen Walker said the brand's retail partners such as department store Neiman Marcus had instantly sold out of the products.
