Currently, there are 25 pets that are listed as drops from Draenor (or other). Additional details about where they come from might be added to the pet journal, but it's always possible that the intent is to keep this information as vague as possible so as to keep us hunting. If that's the case, it'll be up to the community to share and spread knowledge of discovered drops.
That being said, there's already drop information on 3 out of the 25 pets!
Zomstrock - Drops from Soulless Darktide Oracle (and related mobs) along the Forgotten Shore (Southern-eastern shoreline) in Shadowmoon Valley. (source: WarcraftPets forum)I'm in the process of documenting details on the dropped pets of WoD (and will be updating WarcraftPets with this information), so if you know of other sources for them, please let me know!
Stonegrinder - Looted from a chest in a cave off the Orunai Coast in Talador. (source: @perculia)
Grovestrider Hatchling - Looted from a Talador nest in Talador. (source: @perculia)