Where to find a discrete transmission gate
Analog switch is the term Maxim uses, along with lots of other manufacturers.

By the way, the two hardest parts about this type of application are:


high voltage withstand
off resistance at high frequency (i.e. pass-through capacitance)


With the part "off", a sufficiently high frequency signal will couple from the input pin to the output pin, without even going through the switch -- energy always wants to take the path of least impedance.

Transmission Gate is a much simpler structure that is found only inside an IC, I don't think it's offered discretely because of the ESD/latchup structures inherent in getting a signal out of an IC.