Joined up just to answer the most recent post and contribute a bit of my findings, hoping to keep this thread alive!
You won't be able to find a branded source for Arthur's hoodie since almost everything was custom made and then made to look worn in, because they needed several of the same item for Joaquin and his stunt doubles. Only some items were true vintage (and had no potential action scenes).
Here is an interview with Mark Bridges where he mentions that aspect of the costumes. Your best bet is to wait a bit until you can find a maker with a confirmed photo of their product.
I've been working on a sort of photo-diary of creating my own custom Joker suit (I'm a professional tailor) if people are interested in works-in-progress.