I don't know about other regions, but in the US console-specific RF adapters were available separately up to the Dreamcast/PS2/GameCube/Xbox generation, i.e. until HD over HDMI became the prevailing standard (Wii notwithstanding).

For the RF switch part, Nintendo actually recycled the NES design for all of them. It's kind of funny seeing that chunky gray box next to a GameCube logo.