Hi you guys,
Mastermind used to be a source for these but no one is making repro air bags any more so you will have to find good used ones (nearly impossible) or convert to standard shocks.
Click on the link in my signature for a long list of vintage Cadillac parts suppliers.
You may also use the search function above to find other threads on this topic discussing the unavailability of the airbags. Firestone or Goodyear (I forget who) was making new ones until recently but not any more.