Amtrak at selected stations.. + I've bought similar at the KLM counter in the NL Intl. airport
to fly Home from Shiphol/AMS. [less current.. was many years ago]

Out here we pack peoples bikes in standard boxes . at most the rear rack is loosened,
unbolted at the bottom, to get low enough to close the Box..
front wheel and rack and fender are removed, , bars stem seatpost pedals, etc.

[i note you got realistic about the packing, and really dropped the big box Idea..

I have taped together a couple bike boxes, to get things to fit, before..