Odd looking hinge looks like a bolt
Well let's think about this question.
I know it's foam used around the bolt
to keep water from entering inside the car.
Can you buy it probably not but I'm sure
there's someting that will do the same thing
That's just some factory sealer they use to prevent water entry. I would just use some thread sealer, a little bit of silicone on the threads when you reassemble would be just fine.
Never put silicone sealer on any metal parts of your car body. The silicone releases acetic acid when it is curing and will promote rust quickly. Use a weatherstrip sealer or something else.