Amazon.com: Logitech Unifying Receiver, 2.4 GHz Wireless Technology, USB Plug Compatible with all Logitech Unifying Devices like Wireless Mouse and Keyboard, PC / Mac / Laptop - Black : Electronics
Logitech New Logitech Unifying USB Receiver for Keyboard K230 K250 K270 K320 K340 K350 K750 K800 Keyboards - Walmart.com
Logitech 2.4 Ghz USB Receiver for Cordless Mouse (M/N: C-UW34; P/N: 831417-0000) | eBay
eBlueJay: Logitech 810-000908 C-BT44 Wireless USB Receiver for Mouse & Keyboard