I use quite a few varieties, including Apple's, and I have found Belkin’s to be an ideal one — small, secure, with a minimal footprint, and available with a keyring or a lanyard.
https://www.belkin.com/p/secure-holder-with-key-ring-for-air...
That costs more than the AirTag itself.
Yes, these are the best of the bunch. Sturdy too, have had one on my keychain for years now.