If you want to be very creative, you could buy a stamping kit and some titanium washers from microseed.io
Add the washer to a necklace or bracelet, and find a creative way to seal the words. Perhaps apply a thick layer of glitter nail polish over the letters. Why glitter? The glitter will create a unique pattern, so you could take a macro picture of it making it completely tamper proof.
Print out the xpub QR code to go inside the jewelry box. Show them how to import the xpub to a mobile Bitcoin-only wallet such as Bluewallet.
If you decide to put this much effort, you might as well use a hardware wallet to generate the keys offline so it’s a full cold storage necklace or bracelet 🤙
Optional (danger zone): Stamp a short beautiful message on the opposite side of the washer. Have that be a pass phrase.
