The PlayStation Camera for the PlayStation 4 is currently "severely supply constrained," Sony's Chris Norden said today during a presentation at the Game Developers Conference.

Norden, a senior staff developer support engineer at Sony, said the company underestimated demand for the peripheral. He also revealed that the camera has an attach rate of around 15 percent--that's about 900,000 units. The PS4 has sold 6 million units.

The PlayStation Camera is proving hard to find, as it's sold out as numerous retailers. Norden said "please be patient," as Sony works to replenish supply, though it's not clear when more units will be available.

Unlike the Xbox One's camera, the Kinect, the PlayStation 4 Camera is not included with PS4 units. It is sold separately for $60, though GameStop recently raised its price by $10 to $70.