The Forbidden Shirt

With this new update which included the new Legendary Voyage for Thieves Haven, we also received some new loading screens. Inside one of these loading screens seems to be an item of immeasurable quality and worth, as it is the one thing I crave to seek out but have not able to successfully find. This item obviously would be that dashing white shirt with the elegant yellow fabric (scarf thing?) draped around it worn by the gentleman on the right. As far as I have searched, from catalogs of older and now time-gated items to all of the in-game stores, I have failed in my quest to acquire this beauty. I write in desperation to ask if there is any way of obtaining this shirt, as my own voyage for it has ended in failure.