Well, you couldn't trust the device after they returned it. So losing it isn't a problem. The best option is not carrying devices across borders. Have whatever

Well, you couldn't trust the device after they returned it. So losing it isn't a problem. The best option is not carrying devices across borders. Have whatever you need online somewhere. Securely encrypted, of course. Buy a device at destination. And discard it before return. That's accepted best practice for security-conscious firms. They'll provide devices and online storage. If you must carry a device in transit, it ought to be plain-vanilla, with nothing sensitive on it. Again, security-conscious firms supply such devices for staff. And private individuals can just say that they're too concerned about theft to carry their primary devices.