Air tag that shit yo!
Not bullet proof but better than nothing
The main is get one that is well hidden or hard to remove. Experienced bike thieves will know to look for them. I have something like the link below then I filled the screws with apoxy. Makes it a pain when I have to charge it but the point was to make it as hard to remove as possible. https://www.amazon.com/Airtag-Bike-Mount-Tracker-Theft/dp/B09FKNYJNQ/ref=mp_s_a_1_12?keywords=GPS+Bike+Tracker&qid=1642460933&sr=8-12
i use this Airtag Bike Mount Bike Tracker... https://www.amazon.com/dp/B09FKNYJNQ?ref=ppx_pop_mob_ap_share
And here is the other one I use:
Airtag Bike Mount Bike Tracker... https://www.amazon.com/dp/B09FKNYJNQ?ref=ppx_pop_mob_ap_share
I got this and it’s pretty discrete:
https://www.amazon.com/Airtag-Bike-Mount-Tracker-Theft/dp/B09FKNYJNQ