I think I’ve found the best place to hide a tracker on my Brompton: in its front carrier block!
It does require a Pebblebee Tag, as AirTag and Chipolo One are too big to fit. Just make sure to leave a space on top for the locking mechanism to fit.
Edit: I was told that AirTags fit as well, so I guess Motorola Moto Tag might fit too, as I believe they are roughly the size of AirTags.
@astifter @brompton The carrier block itself is made of plastic, this thin metal plate is only used to secure the block to the bike, so I does not shield the tracker. (you can see the metal plate more clearly here https://www.brompton.com/p/736/front-carrier-block)
I originally thought of putting the tracker inside the frame, but then the tracker’s signal would have been shielded.