Try any of the main department stores but particularly
Kustermann by the
Viktualienmarkt.
Or if you are willing to drive 3-4 hours you dont need to go as far as Prague, just any town over the border in Czech Rep will do.
Plzen, Karlovy Vary but especially Czesky Krumlov (stunning town, designated a UNESCO World Herritage Site less than a 4 hour drive). Nice weekend away and get some crystal.