you put a piece of flexible plastic over a normal microswitch. or are you talking about the lights? (add LEDs)
They're standard discrete pieces of acrylic with a diffuser over the top. Each piece of plastic has one green and one red small LED behind it turned on as and when required. The acrylic is attached to the PCB.
Anything that will diffuse the focused beam of an LED. A plexi "light pipe" will work, or if space is limited some sanded plexi can work as well. Also sanding the LED can help, but that won't work for surface mount LEDs.