This is a simple but effective way to make a backlit LED using the common-as-dirt tact switch pushbuttons from Omron and an LED.
It would be very easy to design your own custom buttons for this setup, all you need is a 7mm hole that is 1.5mm deep, with another hole that is smaller than it but larger than the diameter of the LED (I used a 6.10mm hole for mine) that is at least 4 mm deep (to allow room for the LED).
Note that you will need a properly sized resistor in series with the LED to prevent burning it out, I didn't use one here because I was using a constant current power supply for testing purposes.
LED: HLMP 1700
Pushbutton: Omron B3F-1000