You do need to go through the process of elimination. I have a white Jeep, so I went out and bought a big roll of white vinyl tape, similar to electrical tape.
Then I taped off everything
that could possibly leak: the joint between the hard top and the windshield frame, the whole length of the windshield frame, the hinges for same, the weld where the base of the windshield meets the cowling and the one where the cowling meets the hood panel. And I taped around and over the cowling vent. Everytime it rained, I un-taped one section and looked for water in the cab. When I got to the cowling, Bingo! Water dripping in around the cabin vent. So I checked the drain tube to make sure it was clear, and made a gasket for the grille.
I noticed that the opening in the cowling has a down-turn that fits inside the lip of the air box, so rain can't get in that way. Other than a blocked drain tube causing overflow into the cabin vent, the only other way for water to get in is through the screw holes. Fitting a gasket blocked off that pathway, and my cab is now dry.
You may discover your leak is elsewhere, but my advice is to bite the bullet and take the time to diagnose this in a systematic way.
Otherwise you may wind up spending a lot of time and money without result.
BTW - if you look on a Jeep parts diagram, it will show a gasket and a part number - but you can't buy one.