You CAN order rifle boxes from the folks that make boxes. You can also use (and charge for) an inexpensive hard sided rifle case (keep the box it came it- you will need to put it back in box to ship) I have paid as little as $9 each.
Advice on shipping- remove bolt if bolt action. If barrel can easily be removed, do so (like a bolt action) Saves on broken stocks. Pad the ends with about 4-6 inches of Styrofoam or tightly balled newspaper.
Check electrical supply houses- the boxes that fluorescent light fixtures come in can also be used. And if all else fails, check gun shops in your area...