The availability and quality of any kind of merchandise varies widely across the Universe. For starters, lots of neat stuff can be found at the Galactic Trading Post, Chaddy's Intergalactic Junk Yard, the Storage Dimension, or on planets like Urp or Klibbertot, but you have to sort through a lot of junk before you get to it. Here's where to go if you have something specific in mind:
Clones: Conwa (assuming you want your clones to have no emotions), Kamino
Deadly diseases: Buboe
Fertilizer: Antares II, Cowplug VIII
Fluff: Blastus III or your pocket, satchel, seat cushion, etc.
Movie star autographs: Starrywood
Scum and villainy: Tatooine (specifically, Mos Eisley)
Temp-personality transfers: Vega Vegas
Women: Amazonia, Ryloth, Terra Androgena, Zeltros (note: this is assuming you like humanoids, which is admittedly a rather racist assumption for us to be making, but we needed to keep this article at a manageable length somehow)