Do not have FIC locks have Tri-mark, and they have a part that likes to break as well.
I have fixed it two ways: ONE: had a fabrication shop carve me one out of steel instead of the el-cheapo pot metal they used.. Works much better.
The other thign I've done is machine the part down a bit and put a steel backer in on it, that works 100% as well, but takes tools and skills many do not have.
My suggestion is to take two copies of the part, one broken, one good, to a good fabricator and have him make you a bunch out of higher quality metal.