Roof Caulking/Sealant - What To Use?

[Jmsx2]

Hey Gang. I had to remove my Roof Vent Caps and the screw that holds them in place had caulking over them. These caps are the ones that go over the 2" pipe.

I don't have time to get to an RV Center or Dealer before we leave on our trip. I'm sure a hardware store will have something that will work. Looking for suggestions. I don't need a lot so a small tube should be plenty.

Thanks.