1993 Jeep Grand Cherokee Coolant cap cover

I have a vintage 1993 Jeep Grand Cherokee Laredo. Being it's age, there are some broken and missing parts. In this case, I was dealing with a broken cap for the coolant expansion tank under the hood. Being 26 years old, it had cracked and separated at the top surface. Previously, I used some metal duct tape to hold it together which worked but was ugly. I decided to try to do something about it since I am looking to sell it soon. I thought of making a whole new cap with threads but they are a li