Me, too!
I got a black Lock Homburg to wear with DJ at the St. James's shop, and I just carried it on the plane in the very sturdy Lock box. I suppose, if you were daring and conspiratorial, you would mail the box on and wear the hat on the plane. That way you could lie through your teeth to customs and - maybe - get away without declaring:devil:
Addendum: I would not have bought that hat without trying it on first. For one thing, they take great care to ensure you have a good fit, and for another, dealing long distance if you are not satisfied is a trial.