Crate of Bobbers: Murloc Head
Sold by Conjurer Margoss. This is the info i have gathered so far, the locations are found on wowhead, just put them together in one place and added TomTom waypoints to it.
The 
Crate of Bobbers: Murloc Head is a toy fishing bobber added in patch 7.1, purchased from Conjurer Margoss in the Dalaran Sewers using 
Drowned Mana earned through fishing.
Guide awaiting review
Find Conjurer Margoss
Head to the Dalaran Sewers and find Conjurer Margoss at 44.6, 62.0. He is located on a small island to the northwest of Dalaran, behind the Tournament Announcer, and sells mounts, toys, and pets in exchange for Drowned Mana.
Purchase the Toy
Buy the Crate of Bobbers: Murloc Head from Conjurer Margoss using Drowned Mana, which is fished up at his island. Note that there is no confirmation prompt on purchase and the item cannot be refunded, so be careful not to misclick.
Tips
Drowned Mana can be fished at the island where Conjurer Margoss stands, and your fishing skill can be anywhere from 1 to 800 to catch it.
While fishing for Drowned Mana, you may find a
Mark of Aquaos — toss it into the water to summon Aquaos the Unleashed, kill him, and receive a boost that guarantees 1-2 Drowned Mana per catch.Drowned Mana stacks to a maximum of 100 in your bag, so spend them on items before hitting the cap.
