I just talked to the Microsoft store and they said that each of these transceivers are unique and it is not cost effective for them to make new ones for the customers. They do not sell replacements. They told me they could give me the cost of a new keyboard and mouse. It was higher than I could have bought it 3 years ago. If there is nothing wrong with my keyboard and mouse why buy another? So in other words, we are just SOL. Microsoft should have said this at the time of purchase. Another example of Microsoft in action.
Would it surprise you to learn that what you were told about the transceivers being unique is not true? I work in an office where we have a large variety of Microsoft Keyboards & Mice and all the transceivers have been swapable so long as they're of a similar
generation. For example I've got one of the small thumb sized v1 2.4Ghz transceivers and it's even compatible with peripherals that come with the v2. So long as the transceiver type more or less matches it usually works. My advice is to buy second hand to
get your hands on a replacement. Don't give Microsoft any more money as they're clearly not capable of providing support for their peripherals to end customers. I tried contacting them and they wanted around £60 upfront just to speak to someone far more than
the cost of the devices. What a terrible way to treat honest paying customers, you don't get shoddy treatment like that with logitech... far from it.