With rumored due dates coming and going, photographers in front of St. Mary’s Hospital in London and royal-watchers around the globe are eagerly awaiting the birth of the royal baby.

Paparazzi with the winning photo aren’t the only ones who stand to benefit from Prince William and Kate Middleton’s first child. On both sides of the Atlantic, retailers are already cashing in on the much-awaited bundle of joy, creating themed clothing designed to tap into the same mania that surrounded the royal wedding.

“If you were in the wedding industry, you were selling knock-offs [of Middleton’s dress],” says Lauren Levy, the co-founder of New York-based clothing company Magnificent Baby, whose designs feature a distinctive “smart close” magnetic fastening.

In January, Levy says Magnificent Baby started shipping its five-piece “Royal Baby” collection to retailers around the world. The collection features red accents, with gold crowns and the Union Jack.

Customers Eager for Royal Baby Gear in the U.K. and North America

gDiapers, which manufactures eco-friendly reusable diaper covers, has also come out with a  royal-inspired offering: a purple velour diaper cover with a gold embroidered crown, retailing for $24.99.

The company, while headquartered in Portland, Oregon, has an office in London, and says the royal baby frenzy has taken over both countries.

“As soon as we launched it in the U.K., U.S. customers wanted it as well,” says gDiapers communications manager Kelli McCee. She says gDiapers chose purple because of its historic associations with royalty; velour was also selected for its luxe appeal.

McCee says the company only did one run for printed gDiapers, and is close to selling out the royal-inspired option.

Levy says Magnificent Baby’s Royal Baby collection has been especially popular on the East Coast and West Coast, as well as to the north.

“In Canada, it’s crazy. We have a distributor in Canada, and it’s selling all over the place, as they’re part of the crown,” she says.

Magnificent Baby had originally intended to make the collection a limited edition, but Levy says there’s been recent discussion to cut another order as they near selling out.

Levy says she can’t imagine any celebrity’s birth coming close to touching the excitement surrounding Middleton’s baby.

“This is a once-in-a-lifetime event. There’s nothing on this scale that we could come up with and make all this [clothing] that people would be interested in,” she says.

Follow Gabrielle Karol on Twitter @GabrielleKarol