There are numerous bolts used in cars that have a built in washer that does not come off. There may be another name for them, I called them captive washers because they don't leave the bolt.
Every bolt retaining a fender has a built in washer. Every bolt to mount a valance does too.
If I had a picture, I'd gladly post it.
I see what your saying now, so not necessarily a locking washer but more of a built in washer. I did a quick search and seems they may be hard to find, I may just stick with the grade 8 bolt with flat and locking washer for now
