Styro may be a problem but the type of foam that's used to line camera and gun cases might not...the stuff that's sort of like a grey sponge consistency.

One of my friends crates art for international shipments and swears by a type of foam called ethafoam. Perhaps you could find out what size box is common across the world (must be some standardization, eh?) and get a block of the foam cut to those exterior dimensions and custom carve out compartments for the vessel and the book...that way the outer box, which will take most of the wear, could be replaced easily while the inner foam block could be used as long as possible. The foam would also help insulate the object from shock and keep it from rattling around in the box. Hopefully, there wouldn't be a problem with the quaiche tarnishing from contact or offgassing by the foam...I expect that if they use ethafoam in crates that hold these world art treasure, it must be pretty inert.

Best

AA