Good question so rummaged around and the answer is not encouraging. The keyword is 'Sustain', so abandon all hope of finding a case of military ration packs.
Aircraft Spruce Canada 6-7 survival kit (6 persons for seven days ~
or longer!)
Dimensions : 16" x 13" x 6.88 " (40.6 x 33 x 17.5 cm)
Weight : 22.80lbs
Food items:
2400 Calorie Food Bar x 3
Hot Chocolate x 6
Tea Bags x 21
Emergency Drinking Water x 6
FYI
I'm surprised nobody has mentioned the
Terminal Corucopia website yet, Evan Booth has a whole range of survival aids that can be constructed from things purchased air-side.