I only installed the vents on a hip one time, due to the structure beneath having vaulted/cathedral ceilings.
The material was from Owens Corning and I think it was called Vent Sure.
There was another one I found, but my suppliers did not carry it, from Mid-Americe.
Generally, it is NOT advised to vent the hips of that style structure, but better to beef up the Intake Ventilation continuously and then using either an Electric Powered Attic Ventilator or a Solar Powered version.
Ed