You've already learned Toyota doesn't do custom orders; What I did and I recommend you do is ask your local dealerships when they receive their allocations. Mine was every other Tuesday. Check their website those days when inventory updates, it took 2 months for my dealership to be allocated a 6...
Now the question is, do they install the wiring for the power tailgate across the board? If so, theoretically it could be installed aftermarket. Anyone pop a tail light off to take a peek?
I’ve been using the carfax car care app, seems to work pretty well. Has the full maintenance schedules for normal and severe usage, plus reminders for everything including registration, emissions and safety. Automatically pulls service records too.