Shopping in Budapest

"Fashion Street" is the name the local vendors gave to Deák Ferenc u. and yes, it has quite a few good name brand stores. http://fashionstreet.hu/

Deák Ferenc u. ends at Vorosmarty ter (square) which is the head waters of Vaci u. which is also lined with good stores (and not so good), then the next choice would be the lower end of Andrassy ut (below the Oktogon) which is also close by.

Finally there are a few good malls one very near the center of town at the Nyugati train station.

Do keep in mind that these are all better name brand shops ... while I think a substantial percentage of the down used in the world comes from here (thanks to the Hungarian love for pâté) I dont know of a local mfg.

I found you a list: https://www.forbudapestlovers.com/en/best/stores-to-buy-women-s-down-jackets-budapest

Now for things like pillows and comforters, compare the local brand https://pehelypaplan.hu/collections/down-comforters with US prices https://www.thecompanystore.com/down-comforter

Bingo: Local Hungarian and on Fashion Street: https://drk.eu/womens-clothing/jacket/women/ and https://www.tchibo.hu/dzsekik-puloverek-kardiganok-c400048929.html?&pos=0 (it cold and raining and I am bored)