Unbreakcable 360° Protective Case for Airtag, [2-Pack] Airtags Keyring Holder, S

Once inside it will provide a decent seal. Easy to install and remove. What's more, retains the strong signal of the device itself. Compared to the silicon case, it is not easy to out of shape. The embedded clear front cover + TPU case = 360 ° Protection.

eBay