Are you interested in purchasing a traditional Austrian dirndl or lederhosen? If so, Trachten Supermarkt would be an excellent place for you to visit. There are two locations: Weisses Kreuz Strasse in Langenzersdorf (near Metro) and in the G3 shopping resort in Gerasdorf.
The shop in Langenzerdorf has one- and two-piece dirndls in every color of the rainbow, both summer- and winter-weight fabrics, and varying lengths and designs. They also sell accessories such as traditional necklaces, shoes, and purses, plus they have supplies to sew your own dirndl. The store also carries traditional men’s clothing, including lederhosen, and children’s clothing.
The store clerk knew a little English and was exceptionally helpful with sizing and testing the garments.
The prices are a bit steep (my two-piece dirndl cost 170 Euros), but I suspect it’s less than you’d pay at the trachten shops in the 1st district. The Langenzerdorf location is at the foot of the Weinviertel/Weinstrasse, so you can wear your new Austrian gear to a countryside heuriger straight away.