They didn't hang around in bringing that out did they!

Oh, my guess is... CO probably had this thing already waiting in the wings shortly after the BBC started filming the 50th Special and had the design finalized.

Dino.

Hello All, I may have an answer to the "top hat" query. It looks to me to be a differential cup used in remote control cars or trucks.     What do you think?

Oooooh, looks pretty close.

Let's face it, while I'm no toy maker, it seems like a pretty easy one to put out.  92% of it is the same molds for the 3rd and 4th Doctor sonics. They probably didn't even have to do anything significant to the electronics, just add a wire running to the LED.