Best bet is to look for an identical donor knife. They probably all used different thread patterns and sizes. Really not worth the trouble. Figuring out the proper thread and size will be difficult and then sourcing it next to impossible.
Next best thing would be to find a way to jerry rig the one you found or something else. (I had one when I was a kid with a wine cork stuck in it.) Believe it or not Randall used to use rubber crutch tips on their hollow handle knives.
Putting money and effort into a knife like that is only worth it, if it has extreme sentimental value.
I’m not a knife snob, but I am a realist.