There is a major, multi-billion dollar seller now listing on B-Stock Supply who carries these very high end, and hard to find, brands. As you likely know, it is extremely challenging to find brands like these on the secondary market because the brands don't generally liquidate. You've probably seen stories in the news over the years about how certain brands burn their excess and returns products, rather than risk them leaking into the secondary market.
Well, here is a crack to get your foot in the door and acquire these brands.
Here is a link to this seller's storefront on bstocksupply.com: https://bstocksupply.com/luxuryfashionretailer