Seems like all the square buttons I’m coming across use 12V LEDs.
12v LEDs will light up when you power them with 5v, though you
might notice that they are a little less bright.
(larger current limiting resistor ==> more voltage drop across the resistor and less current flow)
If brightness is an issue, swap the wedge-base LEDs for 5v LEDs
or swap out the current limiting resistor.
Unwrap the leads and you can pull out the LED and resistor.
(Yellow 12v LED/socket from Paradise Arcade Shop shown powered by 5v.)
Scott