Customer Service Experts is the main one. They handle a majority of airport shops. Service Sense and Ann Michaels have a few at a couple of major airports
There are scattered ones thru the Kern scheduling site as well. They have a burger chain. Also a coffee sandwich shop thru one of their other companies. If you look at their scheduling site u will find these if still available. In case you are flying thru LAX you can now access terminals 4 thru 8 and the international term behind security but be forewarned it is a long walk!