Wyvern-class ships

I'm running "Pirates of Drinax" and the chapter "Treasure of Sindal" mentions Wyvern-class ships (as part of Admiral Gani Peras final fleet) but I can't find them in Ships of the Reach, Highguard, or Adventure Class Ships. Google even told me: "While the "Sindallin wyvern class ship" does not correspond to an officially recognized or mapped vessel in standard *Traveller* (or *Pirates of Drinax*) lore" Not that I plan on them running into one in this adventure but it would be nice to know what they looked like in case someone asks. Also I might have one show up later.