i usually refer to the heater rubber air inlet boot that is impossible to find as the duct and the 2 cardboard hoses on the side as the defrost hoses. i know realize you mean the 2 cardboard hoses. how much is that? the original cardboard hoses can be had from nissan.cc for $5 a piece. we wont mention how spendy they are on evilbay.
i've also seen people use the aluminum stuff. i have a pair of the original brown cardboard ones that nobody wants. they're missing the rubber boots on the end.
any which way you go i think you need the little rubber adapter boot at the end. maybe not?