You could use a Polymorph spell to polymorph into something like a pseudodragon, and cover both requirements.

I aked a question about this. You can view the question to see the answer. But if you don't want to, the answer was "yes". And since a pseudodragon can't speak, the polymorph spell would be satisfied, too. Obviously, you could find a wand of polymorph if you don't want to cast this spell yourself.

You might not have to make a custom item to make your displacer beast disappear.

Good news! You might actually be able to use a real magic item in the DMG for your displacer beast!

The bad news: it's a legendary item.

The Iron Flask allows you to put a creature inside it and make the creature disappear. There's also a 50% chance that the flask is empty, meaning that you could be able to put the displacer beast inside immediately. It would remove the sighting of the displacer beast, utterly relaxing people. You wouldn't kill the displacer beast either.

The creature in the flask doesn't need to sleep, drink, eat, or breathe.

You might not have to make a custom item to make your displacer beast disappear.

Good news! You might actually be able to use a real magic item in the DMG for your displacer beast!

The bad news: it's a legendary item.

The Iron Flask allows you to put a creature inside it and make the creature disappear. There's also a 50% chance that the flask is empty, meaning that you could be able to put the displacer beast inside immediately. It would remove the sighting of the displacer beast, utterly relaxing people. You wouldn't kill the displacer beast either.

The creature in the flask doesn't need to sleep, drink, eat, or breathe.

You could use a Polymorph spell to polymorph into something like a pseudodragon, and cover both requirements.

I aked a question about this. You can view the question to see the answer. But if you don't want to, the answer was "yes". And since a pseudodragon can't speak, the polymorph spell would be satisfied, too. Obviously, you could find a wand of polymorph if you don't want to cast this spell yourself.