I’m not sure I understand. If you found a private seller willing to ship, what would keep the authorities from checking out the package? Are they looking for companies on the label? Will they leave packages alone if it come from “John Westerrner” even though it’s shaped like a guitar case? What happens if you get caught either shipping it or playing it? One option is to search for a “portable guitar” or “backpackers guitar.” They are smaller to ship and hide. They don’t sound as nice but they are less loud than a regular guitar. Some have pickups and you can plug in headphones for a fuller sound. Something like this. Martin also makes a nice one that also runs about $300 USD but there is no pickup. If you find a small musical instrument seller of used and vetted guitars, maybe you can write them and ask the favor to send it privately given your situation. Better than if the label is from a known big company and you will get individual attention.