(Read more: Highlights from New York Fashion Week)
Since launching in February 2011, New York-based ModaOperandi.com has offered customers the chance to pre-order looks straight from the runway in as little as 24 hours after the show finishes.
Among the brands that have worked with the company before are Marc Jacobs, Calvin Klein, Donna Karan and Oscar de la Renta, said Aslaug Magnusdottir, the company's co-founder and chief executive.
"They know there's a pique of interest around the time of the actual show," she said."One of the reasons that designers like this is that Fashion Week used to be a press event that was very expensive for them, but this gives them a way to actually sell the pieces off the runway."
For consumers, this is a game changer because some runway outfits are typically never picked up by retail buyers who may be wary of taking the inventory risk and thus the items are never produced in mass quantities.
"Many of the looks won't ever be made and even if they do, do they make the size 8 or size 0?" she added. "If a customer really wants a piece, this is the only way to do that."
The service also provides designers with another tool to compete against fast-fashion retailers, who can turn around the latest runways trends more quickly.
"Fast fashion, as you know, works on a cycle of just a few weeks," Magnusdottir said. "At least now with our model, a customer can buy that item and know that it's going to be coming rather than be tempted to buy the item at an H&M or Forever 21 in a couple of weeks."
ShopBazaar, Harper's Bazaar recently launched ecommerce branch, and designer Carolina Herrera have taken the idea of buying from the runway one step further this year. (Read More: On a Quest for Profits, Magazines Court Shoppers)
Herrera will show 50 looks from her spring men's and women's line during American Express' cardmember-only event this season. Of these, Harper's Bazaar editors will select five looks that will be available for immediate purchase on ShopBazaar.com.
"American Express has been creating exclusive runway shows for cardmembers for many seasons now," said Deborah Curtis, the company's vice president of entertainment marketing and sponsorships. "And one thing that we have found out, is that after seeing the beautiful fashions, our cardmembers are inspired and want to have an opportunity to actually purchase the looks that they have seen.