Smitty that is the exact same knob I removed.
My boating buddy bought it for me. It comes with 4 different sleeves and one fit the 3/8" threads on the stick perfectly.
The iron cross looks rad buoy chaser.
Here is a website selling the one I have.
http://www.streetsideauto.com/p/mr-gasket-9628/?utm_source=CSE%2BShopping&utm_medium=Shopzilla&utm_campaign=Shopzilla