Check to see if it's the air bag that's busted or the tubing and fittings that connect to it. I think more often the tubing, Schrader valve, etc. tend to develop leaks/problems than the bags themselves, particularly when just sitting. I did have to replace the valve core in one of my airbag Schrader valves earlier this year, in fact. It would leak down slowly unless a valve cap was firmly in place. That's a simple enough fix.
If it is the bag, you should be able to drive carefully to a suspension shop to get it replaced. These are just helper springs; the leaf springs are able to support the weight of the vehicle safely (though not necessarily comfortably, and they may be somewhat undersized for a long trip if the air bags were installed from the factory).