Dodger

This vendor is unlocked by obtaining the item [item=166242], which is a random reward from Pet PvP. I myself obtained it after ~10 wins. The droprate seems decent, with reports between 5-30 wins being common. Using this item will give you [mission=2122], a follower mission. Completing it gives [item=166243], which will lead you to the new pet battle vendor Dodger.The battle pet vendor is unlocked only for the toon that got the item and completed the mission.

This vendor is to sell the items that were previously Horde only pets in 8.0. To find this vendor you will want to go to 68.96, 17.08 which is located underneath the streets of Boralus. For those who don't have coordinates, and to elaborate further on the coordinates, the best way to find this vendor is to exit the Inn and walk out towards the ocean as if you were looking at flight master's direction. In the water you'll notice a small path made of a wooden bridge like structure. You'll want to jump down and go towards it. Once on the bridge you'll follow it until you travel underneath the streets of Boralus where you'll see some crates and a locked door with someone standing there. You will need to do the mission [mission=2121] for the actual vendor to show up, otherwise you'll see [npc=123169] standing there.

The vendor will require you to win PvP Pet Battles (hooray /s) in order to get the message to spawn. Do note that it could take you 1, 10, 100, or even 1000 PvP Pet Battle wins just for it to show up and isn't guaranteed. If you play only one faction then this might be the only way you can get these pets (I am not 100% sure if they are cageable). If you level a toon on the Horde side you might be better off just unlocking them normally since you might want the paragon pets anyway.

Once you do unlock the vendor you'll be allowed to purchase the following items.

[item=163506]
[item=163500]
[item=163504]
[item=163503]
[item=163499]
[item=163498]
[item=163505]

That's probably the worst explanation I have ever heard of how to find something. To find the NPC simply just go to Siege of Boralus Instance Entrance and from there follow the only bridge that is south from it. You need to have the Shady Message mission from PvP Pet Battles to see the NPC near the doors sitting on the table.