The handlebar-mounted PTT button for the amateur radio on my bike once again went toes-up, most like due to the accumlation of road dust and rainwater over the years. Rather than replace the switch, which would require peeling off a massive glob of hot melt glue and resoldering the wires, I just carved the tops off the rivets holding the cover in place, pried off the cover, and removed the button to reveal the top of the switch dome:

Blech!
The dome flexes outward to contact the (rather crusty) terminals on either side, so all the action happens under the dome.
A lineup of the plastic button, the inverted dome, and the cover plate:

The top and bottom of the dome show some grit: that’s where it contacted the switch terminals.
Wiping the crud out of the switch body, scrubulating everything with contact cleaner, and putting it all back together restored the switch to working order. There’s (once again) a snippet of Kapton tape over the cover holding it in place, but I don’t expect this to last very long:

But it works well enough for now …