Power brake booster firewall grommet??? Help

[bguild]

Okay so I added my power brake booster.. I didnt even think about it but when i pulled the master cyclinder off the firewall and then ran the rod from the booster through the firewall I know have a large space around the rod for air and whatever to get inside my cab. I looked up in lmc and classic parts for a grommet but didnt see anything that stood out.

Do you guys know what I am missing and where to get it.. Any help in the right direction would be great..

BTW this was a used booster as well so I probably was missing whatever it should have to seal that area up. Thanks in advance.