I evaluated an LED backlit push button switch for my Synth project. Well Buying's TC011-A S4 T turned out to be the perfect switch for my needs:
Although called tact switch, it feels more like a push button switch with a smooth pressure point and doesn't have the distinct click of a membrane switch. It's more like a Marquart but with a stronger spring resistance and a more defined switching point. The cap is 11x11 mm, translucent with a white diffusor cap inside (other versions with only square white caps are also available), as well as an ergonomic indent. There are different color options as well as duocolor and RGB available. Unfortunately, the duocolor version (colors can be chosen freely, as far as I know) is a bidirectional setup, where the LED has to be adressed by switching the polarity of the two leads.
The switches can be obtained relatively cheap directly from the manufacturer Wellbuying from China. For a lot of 100 pcs, I paid only USD 0.78 a piece for a single color version.
If anybody is interested, I can post pictures of the yellow as well as the orange version in action. I also have a contact, if somebody needs switches. Meanwhile, they are also available through Mouser, but for a much higher price.
Find an individually addressable four button PCB eagle schematic for single LED type TC011s including the part library:
Important: In case you want to use these PCBs in conjunction with a Schaeffer frontpanel with standoffs (no through hole), the mounting holes on the PCB need to be further apart as the glued on standoffs have quite a large base which otherwise interfer with the routed holes for the buttons.