1965 Barracuda MC conversion to Dual Resevior - Push Rod Question

Small black round grommet, that fits on the end of the pushrod.
This grommet locks the pushrod into the MC.
www.brewersperformance.com has them.

I would still go back to the parts store and tell them the MC is missing the grommet. They usually come with it. Have them check other boxes for one.