I use an Apple Airtag mounted in a bicycle bell housing. You can buy those on Amazon, they’re quite cheap. The Airtag bell looks just like my regular bell. So, I just put it on the opposite side of my handlebars. Means I’ve got two bells, but that’s not uncommon on mountainbikes anyway.

You can track the bike using your iPhone and the Find My… network.

There’s some caveats to it, obviously. You need to have an iPhone for one, and the tracking works best if you’re in an urban area with lots of other iPhone users nearby. It’s not an actual GPS tracker, but rather gets pinged by bluetooth from nearby phones which report the location. Another caveat: they start to chime after x amount of hours away from your phone, as an anti-stalking measure. But you can just disable the speaker on them if you want to.

The overall benefit is that they’re quite cheap and require no additional data plans or sim cards.