There are SEVERAL different types of lock nuts. One of the most common is called a "flex" locknut. It has no nylon in it. The flex are found on older exhaust manifolds. Fastenal should have them.

 

Old trick if you can't find a locking nut.

Take a proper size nut, put it a vise and gently squeeze it until it is slightly oval. Doesn't hurt the threads but is a little work to get on. Should hold though. I've done it at work a few times.

 

will thread lock not work????

 

Yep you bet. But it won't be quite as reliable as a locking nut. I've seen supposedly permanent loc-tite not hold in certain situations. Best solution use both.

 

If possible, you really should see if you can use a slightly longer bolt and "double nut" it. We use two nuts on pretty much every crucial part of our race car, and havent been let down. Hope this helps!