Nintendo will be offering players a chance to obtain the 3DS peripheral.
http://www.nintendoworldreport.com/news/28737
The 3DS Circle Pad Pro is available for pre-order at Nintendo's online store.
Originally, it was revealed that the peripheral would be a GameStop exclusive. Nintendo is now offering the option to pre-order it online through their store. The price is $19.99.
The Circle Pad Pro adds a second Circle Pad and additional shoulder buttons to the 3DS, giving some games an alternative method of control. Some of the confirmed compatible games include Resident Evil: Revelation and Metal Gear Solid 3D.
The 3DS add-on will be released on February 7.