This is for questions relating to both the RPi A & B 26-Pin GPIO (and P5) connector Audio Input/Output card originally made by Wolfson Audio who were acquired by Cirrus Logic and the subsequent version for the later 40-Pin GPIO connector A+ & B+, and latterly, 2 models.
Both of these are available at Farnell (Element 14/CPC) - UK Official Vendor for RPi. Note that the first requires a connection to the P5 header which is only present on version 2 of the A and B Model RPis.