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
Wireless Dongle Receiver Unifying USB Adapter for logitech Mouse Keyboard Connect 6 Device for MX M905 M510 Keyboard K400 - AliExpress
Logitech K400 Usb Unifying Receiver - Wireless Dongle Receiver Usb Adapter 6 M905 - Aliexpress