The blue-and-white striped shirt might be the most affordable item of clothing worn by the prince yet

By Monique Jessen
Updated July 28, 2016 10:30 AM
Matt Porteous/PA

In adorable stripes and whale-themed sweaters, not to mention that cheeky grin, it’s easy to see why Prince George is a miniature style icon.

Just hours after his official third birthday pictures were released by his parents, Princess Kate and Prince William, fashion brands chosen by the couple have been working tirelessly to keep up with the famous “George Effect.”

“We have been working non-stop to keep up with demand,” Bunty Stokes, marketing director of Sunuva, tells PEOPLE, adding that online traffic has increased “by over 500 percent” since George wore their 100 percent cotton, blue-and-white striped T-shirt in three of the four photos released on Friday.

And it might be the most affordable item of clothing worn by the prince yet – at just $12! From the brand’s 2015 collection, the casual top, which was originally $37, sold out almost instantly. The beachwear brand, known for their stylish SPF 50 swimwear has been working ever since to get the item back in stock.

A pre-order page on their website for the newly named ‘Sunuva Prince George T-shirt’ currently has a wait list of more than 100 eager customers. Delivery is estimated to be 4-5 weeks. Sunuva ships to the U.S. for an extra $26 – not a bad price to pay for the royally-approved shirt!

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The company has also chosen to honor the sale price, not only on that exact color option, but for all colors of the striped top. “There has been so much interest and we felt the right thing to do is to make sure that our customers could buy the T-shirt, at the outlet price, whatever the color,” Stokes explains, adding that although sales are doing very well in all colors, “Everyone wants the exact T-shirt George wore.”

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Emily Cohen, who founded the company in 2008 with her business partner Sabrina Naggar after noticing a lack of stylish, sun-safe swim-and beachwear for children, says she has no idea where Kate bought the top or how she heard of the brand. “I know that she is a very big supporter of emerging British brands, and with her impeccable taste, to dress him in Sunuva was beyond flattering for us!” she tells PEOPLE.

Celebrity fans include Gwen Stefani, Madonna and Victoria Beckham, but Cohen says she has never experienced anything like the excitement of the last few days. “When it’s the prince, it’s on another level!”