Just curious as to why? I'm a DIY guy myself and just bought the vent and scoop from primitive racing. Its not the OEM one as I have a rally car, but the spec c one is already tried and true.
I just think sometimes its better to get one that's made instead of racking my brain when I can do other functional mods to the car.
If your gonna Fab a "clean" one your gonna have to also mold in the headliner/flap handle. And perfectly seal it.
I'm not trying to sway you either way. Just trying to give you another point of view.