Amazon carries something that might work for what you'd like. I'm assuming that's a patch on the duck's jacket though and not a pin though. But this pin, albeit small, is pretty close to what you're seeing.

Personally though, if you're open to something which isn't a pin, this ring looks kinda nice, IMO, and wouldn't cost a lot for a gag item. And this pin could be great for St. Patrick's Day.

So yeah, just do a quick google search or so. That's basically what I just did.