With a little of observing, and until I realized the importance of Lock Nuts, Spring Washers can be a substitute for Lock Nuts! As I write this post, I checked on Wikipedia for their own definition of the Spring Washer (also known as Split Washer, Lock Washer). It exerts force on the sides of the washer and make friction to stop them from rotating. Compared to a Lock Nut, Spring Washers requires 2 objects to work (a plain washer on 1 side and a nut on the other) while Lock Nuts can remain stationary all by itself.
I asked a fellow racer on how does he use the Spring Washers. He uses them as adjustment of the height of the brakes.
So the next time you ran out of Lock Nuts, check if you can use a spring washer and a nut as a substitute.