If you haven't already, you might post this in the Case/Ingersol forum. The sites that i used to follow for Case have closed down. But somewhere there could still be some activity...especially in the northern States.
There is a guy who sells used Case / Ingersoll parts in southern Michigan. He advertises on Craiglist from time to time. I'd look there to find him and see if you can get the parts you need from him.