Issa Girls: Madonna, Eva Mendes, Katy Perry and Kate Middleton | Getty Images

Less than a month after Kate Middleton caused a retail frenzy by stepping out to announce her engagement to Prince William in a royal blue wrap dress, its designer is positioning herself to become a global fashion brand.

Gallery: Royal Wedding Details

London-based designer Daniella Issa Helayel plans to start that expansion by making it easier for non-royals on this side of the pond to score some of her in-demand bright and fluid frocks. She's updating her web site to include e-commerce in the United States sometime in 2011, she tells WWD. Click!

Also coming: A "Baby Issa" line for tykes (and maybe a future baby royal?) and six freestanding boutiques in Helayel's native Brazil.

The designer told WWD she was "flattered and honored" the future princess chose her dress for such an important occasion, especially since her line's beginnings were so tenuous. The first Issa collection, unveiled in a 2001 Paris fashion show, was a commercial flop. Just one Brazilian retailer picked up the line. "I cried," Helayel told the newspaper.

These days the tears are more likely shed by shoppers trying to track down sold-out replicas of the Middleton frock.

While Barneys, Intermix and e-retailer Net-A-Porter have stocked Issa stateside, its vibrant hues have not been readily available beyond its London base.

Helayel gradually built the brand cultivating a modest celebrity following with a few high notes, namely Madonna wearing one of her dresses during a 2006 Oprah appearance. She now counts actresses Scarlett Johannson, Kiera Knightley, Eva Mendes and model Naomi Campbell as fans.

Helayel, of course, had her biggest moment when Middleton (already a fan of the line) slipped on the flattering dress for her first official appearance as a royal-to-be at her Nov. 16 engagement announcement.

The dress quickly flew off the shelves of London retailers and was quickly solid out when Net-A-Porter offered it for special order stateside.

Meanwhile, read about the similar reaction to the creamy clothes by Reiss and Whistles Middleton chose for her official Mario Testino engagement portraits.

Gallery: Royal Engagement Portraits

And read about the negative reaction to the future king and queen's images on their Royal Mint engagement coins.