WANTED: giant rectangular tree or appliance boxes (East Austin)

As the heading states: I am in need of some very large cardboard boxes -- like giant sticks of butter.
I have one from an artificial xmas tree that is perfect (it's 48" x 13" x 15").
Larger would work.
Flattened boxes of this size also good.
Perhaps you have some giant Xmas present cardboard I could take off your hands? It is for a parade float installation, so smaller boxes won't work.
I'm available to pick it up this week.