i don't think it is supposed to have any type of gasket. in the front of the scoop there are 2 little cutouts for water to drain out from under it. a gasket may cover or block these cutouts preventing the water from coming out leading to a rusted hood. the only gasket i know of is the 2 donut gaskets that fit the factory round holes in the hood. this keeps water from draining in on the top of the engine.
I used some of the thinner self adhesive window/door insulation sold at hardware stores. After I tightened down the stud nuts you couldn't even tell it was there.