ATT -> Outdoor Zones -> Zandalar -> Dazar'alor -> Vendor -> Oily
Need to add alliance vendors to the tooltips for 3 of the pets. The others are showing the alliance vendors.
Abyssal Eel - Madeline Netley - Stormsong Valley
Greatwing Macaw Feather - Dana Pull - Boralus
Strange Looking Mechanical Squirrel - Dana Pull - Boralus

You don't see them on your Horde character because these vendors are hostile to Horde. You see Nigel Rifthold because he is friendly to both factions. If you enable Debug mode you will see that all vendors are there.