IIRC, that clamp is welded to the collector. (My bike is @ home and I'm @ work.)
As mentioned, you can buy Holeshot's header to go with your new mid-pipe & can. OTOH, if you didn't really want to spend that much money, you should be able to get it fixed by a good muffler shop. They should be able to remove the existing clamp and attach a new one - or you could go with some kind of clamp that doesn't have to be welded on.