SparkFun COM-09808 Locking Button – Medium Red Panel Mount
This is a very useful panel-mount locking button/switch.
Press it once for 'on', once again for 'off'. It is a SPST N.O. with 7/16" threading.
This button has a nice 'click' when you press it. It would work best in low-current applications. Overall length (including leads) is 3.9cm and has small solder lugs for connection.