NitroX
Huntingtons has 20 round plastic boxes that will hold 450 No2. Also the biggest MTM boxes will hold 50 450 No2's even when loaded with 500 grain Hornadys.
That does not help you now. The main thing the airlines want is some sort of packaging that seperates the rounds individually and offers primer protection. I always lock my ammo in a small Pelican case. You might could get by with your ammo in your belt ctg holders if they were placed in a Pelican or some other hard lockable case.