I think the device in question is described in US Patent 3,437,165 "VENTING DEVICE FOR PRESSURIZED SPACE SUIT HELMET" (filed Feb 27, 1967). It is possible that NASA did not file immediately for patent, especially when the port was eliminated. Hamilton Standard is listed as government employee on the patent form.
The patent can be found in NTRS under the following link:
The apparatus is described as
A venting device comprising a fixture mounted in the faceplate of a crewman's helmet for use with a pressurized space suit, wherein the device incorporates valve means providing controlled venting of the helmet in the oral-nasal area and incorporating a collapsible duct or funnel positionable between a collapsed stowed condition adjacent the faceplate and an operating position in which it projects into abutment with the mouth of the crewman
for elimination of vomitus expelled by the crewman.
Illustration of the port:
The aforementioned PDF contains some more close-ups and technical drawings of the inner workings of the mechanism.