score:7
In the end I was able to find what I'm looking for by traveling to a pharmacy in one of the big shopping malls (Emaar Square Mall), which had a section with food supplements that I was looking for. I guess the answer is thus to travel to the nearest large shopping mall instead of trying local pharmacies in downtown Istanbul.
Upvote:2
Cover the counter pharmaceuticals are also sold online in Turkey and a lot of pharmacies list their inventories there, hence uncommon stuff also appears. Then one can either contact the stores individually or just order online. Few potential webpages to look,