I was just on the Polarware site as I'm considering a new brew kettle. Low and behold I just saw this "party barrel". At 31", I think it'd fit a 6.5 carboy with airlock would totally fit. You could probably drop a couple bottles of frozen water in there for a nice chamber. I wish I hadn't just bought an Igloo cube cooler to modify.
http://www.polarware.com/home-brewing/party-barrel.php