There are many businesses that sell mankenler (mannequins), concentrated on Irmak Cd (Avenue) in the Bülbül (nightingale) neighborhood of the Beyoğlu district. These are a few images from the storefronts.
As I was taking a photo through an alley doorway out back, a gentleman invited me inside to look at where they finish the product in that particular establishment (below). It was a small space.