A free tow to the BMW dealer- if they are closed they will bring the car there the next business day. Then you hope the dealer stocks that tire- which they will not since it isn't a runflat.

(I carry a full size tire in my M5 (which is designed to use a pump and slime)... it has saved me many times. Rather not wait for a tow truck, and get hauled to a dealership in the middle of the night. Jack it up, on my way in 20 minutes.)

Anything I can do to rely LESS on other entities (BMW assist, roadside assist, a dealer stocking the correct tire) make me feel more secure.