A button or pin is a great idea! Far more likely to be worn on every hike than a shirt. You could even put it on the shoulder strap of your pack, so it's always there and you'll never forget to put it on.
However, I for one would still like to have a shirt too.
"Come visit us again and again. This is a state of excitement. But for heaven's sake, don't move here to live." Tom McCall