Gameplay.co.uk have the Official Sony PS3 Wireless Bluetooth Keypad in stock for £17.99 including delivery. This is the cheapest price I've found anywhere (most places have these for £20-£30).
This is the keypad which clips over the Sixaxis/DualShock3 controller for the PS3.
The keypad features two shortcut buttons; a Communication button and a Message Box button, letting users jump to pre-set features on the XMB such as the Friends screen and the Message Box during gameplay. The Touch-Pad button allows PS3 users to use the surface of the keypad as a touch-pad, allowing them to move the pointer whilst web browsing by sliding their fingers around the keypad surface.
Gameplay have had this advertised at this price since its release but they never have stock. Order while you can.
P.S. First post so sorry if I've missed anything out.