We noted on our hotel reservation that we were celebrating our engagement and we got our pins at the hotel when we checked in. However, I'm pretty sure that you can get them at any guest relations desk if you just ask. We've had a few other "celebrations" throughout the years and the people at guest relations have always been wonderful in giving the pins.
Third-party vendors do sell them on sites like eBay if you want to pay for them. Just make sure that you get the ones for the park you plan to visit, if you care. They'll say either "Walt Disney World" or "Disneyland" at the bottom of the pin.
I was told by a Disney pin collector that they were doing away with the "Just Married" buttons. Has anyone else heard of this? Is there any truth to this sad rumor? Thanks!