Amazon.com: Logitech USB 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 MK520 Wireless Keyboard Mouse Combo with Unifying
For Logitech K800,K750,K710,K700,K520,K400,360 Unifying NANO USB Dongle/ Receiver | eBay
Logitech MK520 Wireless Keyboard and Mouse Combo - Black | Dell USA
Logitech MK520 Wireless Keyboard Mouse Combo with Unifying
Logitech K520 Wireless Keyboard (NO RECEIVER) (NO BATTERY COVER)