Kate Middleton's sapphire engagement ring wasn't the only blue item royal watchers were talking about this week.

Immediately after Middleton -- and new fiance Prince William -- stepped out in front of the cameras this week, women rushed to buy their own $620 Issa garment.

"Since the announcement of the royal engagement we have been inundated with requests regarding Issa," Averyl Oates, the buying director for department store Harvey Nichols, said. "The dress worn by Kate sold out almost immediately."

Meanwhile, ABC News reports The Natural Sapphire Co. was also swamped with orders. Those eager for a replica of Princess Diana's former ring crashed the New York's company's website within minutes of seeing it on Middleton's hand.