I bought about 4,000 earring backs from a craft store and set out for Go Fish! in Brooklyn to find some cheap vintage buttons. The buttons were ridiculously cheap and ridiculously awesome. I lalalalalove the color and plaid texture of the Bay Blue Buttons. The Wedding White really stand out when you wear them, and they also have a very cool texture. The Galaxy Black Buttons are shiney and swirly.
Some of the buttons I bought had metal protruding (to be sewn to clothing, in the normal fashion for buttons). I broke the metal with pliers, and the earring backs were big enough to cover over any dangerous metal shards. All I did was apply hot glue, and Voila! Kathleen Vintage Button Earrings a-go-go. I bought extras in case they broke; and while only one actually broke so far, an unforseen Wedding White earring and black eye makeup also rendered the spares useful!