How long would it be out on the table? I've seen people put it in a stainless steel container that was kept in the freezer until it was ready to be served, and then nestled in a larger container full of crushed ice. It kept for about an hour before it was too soft to eat. I'm not sure what to do if you need it to be out longer though.
ETA: Dry ice may work even better, but I've never seen that done. Not sure if you've used it before of course so at the risk of sounding obvious, use gloves if you go that route because it can burn skin quickly.