I guess this type of Keyboard is not too popular.
I found a used one on eBay and it works just fine, so I'm good.

If anyone comes across this post in the future and wants to have any of the WebTV Keyboard mapped, post a request and I'll get it for you.

I have an Arduino UNO with a TSMP98000 IR Sensor and a working copy of IrScrutinizer-2.4.1 that seems to be able to decode anything IR.

S.M.