Just an observation (happy to be corrected if I have this wrong) but you will be unable to get an AirTag into many typical road bike setups.
This 31.9mm diameter size is larger than the common 27.2mm round seat post diameter found in a majority of road bikes. That’s even before considering that your design fits inside a post, which would mean an even smaller diameter available.
Even the example you show with the Domane post above won’t work since it is smaller than 1.25" per the graph paper trace. The potential pool of compatible bikes/posts will likely be restricted to bikes with non-round posts, which means aero road bikes and TT/Tri bikes for the most part.
With that in mind, I do have another concept that could be worth considering, that would possibly allow for one insert design to fit multiple posts designs and sizes. I can model something quickly if you are interested.