I didn't even think of this until Hypnotic was sold, but if anyone knows of a guild with the Thundering Serpent Hatchling that is available for sale or trade, hit me up through the website or in-game. Ideally I'd like to get a guild and move it over to Madoran so people can get the pet and we don't have an overcrowding problem in the pet guild.
You've probably already thought of this but have you popped an advert on the WoW forums? Including the Oceanic ones? I've been seeing a few lvl 25 guilds up for sale lately but didn't think to see whether they had the pet available!