Looking for well-stocked gardening supply store

Hey all,
  Been living here three years, and am finally converting rooftop to garden.
  I need to find a good, Western-style nursery/hardware/garden/home-improvement store (a la Home Depot/Lowe's) or any combination of stores that will have similar ranges of stuff.
  In particular, I need to find vermiculite and Perlite, two minerals used in the fussier sorts of gardening.  Failing that, rye seed or wild bird seed might work for one of the projects I have in mind.
   I've checked numerous VNese nurseries, and been met with blank stares.  One might have had Perlite, but it was unlabeled, so how could I be sure?  Any ideas or advice you have will be most appreciated.
   Cheers,
   CAExpat