Buy a box of cotter pins (cheap) and use a new one each time. I suspect that NylokŪ nuts might not work well due to brake system heat, either coming loose or melting shut.
Perhaps the safety pins we use on aircraft could be used:
https://www.aircraftspruce.com/catal...owlingpins.php
Here are some other locking pin ideas:
https://www.mcmaster.com/lock-pins/cotter-pins/