We had one 3D modeling and printing guru at my last place of work. Our machine had 'good' resolution but probably not on par with the current 'best'. Regardless, I think he/it could have produced a decent-looking part (albiet with some texture) that would handle way more heat then the woefully inadequate stock vent material. (iirc the extruder temp setting for PLA plastic we commonly used was something like 180C).
I tried to disassemble a distorted vent today and found that the two large parts illustrated in Mike's photo seemed inseparable w/o breaking something. They probably aren't literally 'fused' together but I realized they could be modelled & printed as a single chunk in the assembled state shown below. Seems like a sensible shortcut but I may be missing something!