You can purchase replacement ribbons mounted three to a frame, but that's not the way they're issued. If you look at the photograph of Kerry at the event, you can see several independently attached bars, at least. He could not have easily removed them with one hand.
You buy the frame and slide the ribbons on. I used to have a three row frame (9 ribbons) mounted with two pins. You can buy the frame to match the number of medals mounted. I haven't examined the photograph that closely nor do I know what Kerry wore to the tossing of medals event and how easily he removed them. The point is he threw something away and no one knows for sure what it was.