We use a Polar Bear backpack cooler
and it seems to be head and shoulders
better than others. Plus, they offer a
TTOL discount.
We use dry ice the night before and
transfer all (except any remaining dry ice)
to the Polar Bear just before
heading to the airport.
Completely fill all air space with food
or something and don't open the cooler
for any reason other than a requirement
by TSA.
Stuff will arrive frozen rock hard.

Mike