The parts websites list the same model shear bolts for both the augers and center impeller. Several people report success using regular Grade 5 bolts and lock nuts, these have a little more "give" and are less likely to snap immediately from a sudden shock, but will still give way when jammed completely.
Almost have to wonder if the pins breaking are a sign of something else wrong with the impeller? Any sign it's scraping against the housing or loose?
Bobcat 3650: Material Bucket / Snowblower / Snow Blade / SBL 30" Light Bar