I've found that most stores that ARE NOT selling fasteners outright have a VERY POOR idea of what is needed for any sort of job. SOmetimes there are surprises in some of the chain stores that you actually find what you want.

Add Grainger to the list of vendors for hardware and fasteners. Old time local hardware stores are the best for most hardware but some suffer badly at stocking metric anything.

Sockethead bolts are typically of high quality so that isnt a worry like many hex head fasteners. Watch out for the finish. Common black oxide finish rusts the worst. I always paint them if I have to use them.

-SP