"Little Princess" Costume

The "Little Princess" Costume is one in a series of costumes for the Perky Pug.

Source
Purchased in a set of five from for 500x Timeless Coin on the Timeless Isle.

Additionally, the following vendors sell them in exchange for 1x Pet Charm:
 * Lio the Lioness, Lunarfall and Dalaran (Broken Isles version)
 * Serr'ah, Frostwall and Dalaran (Broken Isles version)