Pre-order the ElevationLab “TagVault” Waterproof Keychain Case for the Apple AirTag
Shipping later this month (June 2021), ElevationLab's upcoming TagVault is a compact, durable, and waterproof keychain case for Apple's “AirTag” item-tracking gizmo that protects the device from scratches and other abuse while still allowing its speaker sounds and Ultra Wideband signal to pass through unhindered.

It goes without saying, but: keys and keyfob not included.
What's nice about it is that, unlike this type of keyring, the TagVault doesn't advertise that it's hiding anything special inside. And even if a prospective thief has an idea of what's in it, they'd still need a specific Torx wrench to crack it open, and by the time they get one, you've likely already tracked wherever they've taken it.
The TagVault can be pre-ordered now from ElevationLab at $13 for a single, $40 for a 4-pack, or $75 for an 8-pack.