If you've taken trig. or geometry and have some cardboard, u can build one like mine..
first draw out a square for the fan and a circle in the center of it.
draw 4 trapazoids connected to the square shape to fit the heatsink
so basicly if you're using a 92mm fan, the top piece of the trapazoid would be 92mm and the bottom would be 99mm
thats for the left and right sides
for the top and bottom, it would be 92mm to 59mm.
you gotta deal with the angling as well, if ur good at math, u can do it like that, if not, you can just make'em all with 45 degree angles and cut bits off and use trial and error.
i'm going to be making one tomarrow for my blower so i'll try to take pictures
make sure u use thick cardboard, not too thick, but something for good support
u might want to use washers as well to screw in the fan, unless u plan on gluing it on there.
after u finish it, tape all the trapazoids together, you'll probably want to tape the shroud to the heatsink as well to prevent air from leaking out.
i'm not sure about the 94's fan mounting style is, but try to accomidate the shroud, like but putting holes in i, so you can provide extra hold with the mounting stuff, i wouldn't rely on just time, but that is what i'm doing now.
BTW, i would recommend using black tape.
yes i know and i think it works too, but the shape is just confusing me, since the air would (in width) be focussed on the center of the HS (good) but the air (in length) would be focussed over the HS and beyond it :/ got any piccies, because maybe im just not getting the picture here lol