Microsoft no longer hosts the tool on official download pages, but it can be found via:
The v1.0 UPD transceiver is designed to work with a wide range of Microsoft devices. If you have a Microsoft Keyboard and Mouse that both support the 2.4GHz Nano protocol, you can often pair both to a single transceiver, freeing up a valuable USB port. This interoperability is fantastic for decluttering a workspace. microsoft nano transceiver v1 0 upd
Older versions of the driver identified this device as the "Microsoft Mouse and Keyboard Detection Driver (USB)" (e.g., v8.1.239.0). Where to get updates: Microsoft no longer hosts the tool on official