From what little bit of information I can find, it sounds as though the Darkmoon Hatchling comes from the ticket vendor -- just like the existing Darkmoon pets. The Eye pet comes from RNG (boo) opening "Darkmoon Pet Supplies" when you beat a new tamer inside the fairegrounds. And the Glowfly pet wanders around and can able engaged as per normal wild pet hunting. Supposedly.
I was wondering if anyone happened to have easy PTR access and would want to verify any of this? Like check it out and see if they can indeed get the Eye to drop from the bag or check and see how many Glowflys are up, how bad their respawn rate is. How many of them wander the island.
I may end up getting a chance to check it out myself later in the week -- but I'm sure some other pet enthusiast will jump on it sooner. If I find anything helpful out I'll add to the thread. Super thanks in advance if anyone checks this out.