Do you want the box to display or a hard copy of the installer?
If the latter I’m sure I’ve seen them for sale in the past couple of years on distro websites. Click “get [distro]” and its some secondary item to downloading which is what most people went. Might be a USB key or disc.
If you want an actual box idk how they are shipped.
How curious. Are you doing a play?
You might have to DIY one if you don’t want an old one. Certainly there are websites you could upload a PDF to that would print for you.
I think the boxes made sense when they were for sale in a brick n mortar store because they are harder to steal and make the person feel like they are buying something when digital goods weren’t such an instinctive idea. I doubt they would be shipped because they are big for no reason and would require a lot of packaging to keep from getting wrecked in transit vs a USB key in a bubble envelope.
To buy linux in a box, you would have to find somewhere near you that is selling it in person. A computer store, a book store. Maybe a campus bookstore? They have a captive audience so sometimes can get away with stuff that doesn’t otherwise make business sense.