Alternatively you could cut the entire plug off and solder on a new
1/8" (3.5mm) mono plug in it's place, just leave the mic wires disconnected. This would look much nicer, and the smaller plug will reduce stress on the jack.
P.S. If you don't want to modify the speaker/mic's factory plug, then you could simply use a [short] 1/8" extension cable as well.