This product is either discontinued or we cannot get that from suppliers.
Poly Plantronics 211423-04 Savi Spare Headset And Charging Cradle, Black, Wireless DECT, Sound Output Stereo, Impedance 32 Ohm, Microphone Boom, Controls Mute, volume, on/off, answer/end.
The Poly/Plantronics Spare Headset and Charging Cradle 211423-04 is a replacement part and accessory which is specifically designed to fit and work accurately with W8220 (and -M).