If you are looking for moving boxes, not shipping boxes, I've known people to buy refrigerator boxes, cut them down, seal with packaging tape and pack foam / bubble wrap around the speakers inside the box. If you think you might ship them, then I'd want an original box. Shipping will put a lot more stress on the box.
I still have the original boxes for my VR-4s from 1995. They've been through 5 moves, being shipped to VSA in California for an upgrade, and a flood. They are very gnarly, with the cardboard starting to peel off. Thinking about finally ditching them. Just used them again 2 months ago.