Best Buy: Logitech USB Unifying Receiver 910-005235
Amazon.com: Logitech USB Unifying Receiver - Black : Electronics
Unifying Software – Logitech Support + Download
Logitech C-U0007 Unifying Receiver for Mouse and Keyboard Works with Any Logitech Product That Display The Unifying Logo (Orange Star, Connects up to 6 Devices) - Walmart.com
Logitech Unifying Receiver for Connecting Multiple Devices