Did no one at MS respond to you? I am in the same situation!
Wireless Keyboard Dongle replacement

Eugenie Rice
6
Reputation points
In July 2021 I purchased a Microsoft Wireless Comfort Desktop 5050 UK Qwerty Keyboard for the amount of £49.99.
Just over a year later and the Dongle (which has been held together with sticky tape for the last few months has finally fallen apart!
From looking at forums it appears that a replacement dongle is not available and I need to buy a completely new keyboard.
Surely this can't be correct?
I can provide all the relevant product codes and all the serial numbers on the circuit chip inside, all I need is a replacement!
Let me guess, it has a one year guarantee.