New to me Monarch 12 CKK, help needed

I just picked up a 1944 12 CKK last week and have been doing the usual cleaning, changing oil, etc... I need help with one of the knobs. Somewhere along the way the knob for the quick change gear box lever went missing. The previous owner made a knob with a stud that holds it in place but it can vibrate out. I want to make one like the original with spring loaded plunger so it will stay in. I'm hoping someone can provide me with some pictures, plans, or measurements of this knob/plunger assembly. I called monarch about it and Steve told me the knob was different in size than the other knobs but I could buy one for about $1000. I think I'd rather make one for that price. Any help or advice would be appreciated. Thanks

Bob...

From the 12CK manual