I'm having a hell of a time finding a CIH shift knob, but I did find one that had the old IH logo.
IHC IH INTERNATIONAL LOGO ALUMINUM GEAR SHIFT KNOB #186 | eBay
You could try calling Hoober's, they are the largest CIH dealer on the east coast, I'm betting some of them would be willing to search high and low to find something like this, or they might be able to source one easily.
Tractor Parts from Hoober, Inc: Case IH, AGCO, Kubota, Krause, more
The best part is, everyone who works in the company is enamored with Case, IH and NH. I worked there for a year in the IS department, but I couldn't wrap my head around the Case love...