hmm- they have them in with the 'findings' - earring loops, barrette blanks, that sort of thing...

or are you talking about a particular KIND of pinback? I know the commonly available ones are uglier than sin, and in some cases, I've turned my own rather than use them...but when I'm making $5 pins, putting $3 into the pinback doesn't work.

http://cgi.ebay.com/24-SILVER-Pin-Backs-1-25-pin-on-Favors-Capias_W0QQitemZ5603978863QQcategoryZ3268QQssPageNameZWD1VQQrdZ1QQcmdZViewItem

The ones I have made look like a cameo pin. The cross stitch goes in the center. They are quite lovely. Who would ever know I couldn't find more when I needed them.