As far as I know any standerd wireless keyboard that uses a usb adapter should work, when I had my PS3 I was temped to get this,
Keysonic RF Wireless Keyboard w/ trackpad
• Wireless mini-keyboard with built-in touchpad and 2 mouse-analogous function keys
• Powerful and reliable radio-frequency transmission at 2.4 GHz
• Enjoy free and independent choice of site up to approx. 10 m away from the PC when operating this keyboard!
• Extremely flat construction with built-in hand cushion for non-fatiguing work
• Full functionality of a standard layout keyboard due to built-in numeric keypad and 12 function keys
• Extremely silent stroke and tactile feedback due to high-quality “X-Type” membrane technology
• Hot Swap and “Plug & Play” installation without special driver
• Ideal use for: home theater, conference and presentation facilities and mobile applications, as well as for modern office environments.