Hatch gasket problems\Mositure in car.

My 96 gsr has a lil problem. When it snows or rains, moisure ends up on the inside my hatch's glass. I look on napaonline to see if they sold a whole new gasket that goes around the hatch, but they don't. Any of you have this problem? Can you think of how ti fix it without me having to go to the dealer and pay like $200 to get a factory gasket?