First of all, as one record shop owner told me, it is now very much a trend for young turkish people to seek out these old gems, previously a pursuit of only a few savvy western collectors. So don't expect to go and find OG rarities in the flea market (at least ones in decent condition). Those days have gone.
Off the top of my head, the most sought after artists are Baris Manco, Erkin Koray, Ersen & Kardaslar*, Selda*, Mogollar, Cem Karaca, Senay, Okay Temiz and Uc Hur El. Basically everyone is looking for records by these guys, so expect them to be priced highly when seeing them on the wall of a record shop
The record shops in Istanbul are located in two distinct regions; Beyoglu and Kadikoy. 90% of first-time visitors to Istanbul will be staying in the Old City (to be close to all the mosques and old shit), so Beyoglu is a short tram ride + walk away (or just a decent walk away), whereas Kadikoy is on the Asian side so you need to get a ferry over there (very easy). Here follows a few words about each one, click the name and hopefully the approximate location will come up on google maps
This is the first area I visited. The first shop to check is near Taksim Square called:
Plakhane- It is worth mentioning at this point that Google Maps almost always shows you an incorrect location for many places in Istanbul, it took me ages to find this damn place. There was one small stack of Turkish LPs here which contained mainly chud. 45s were a bit better organised and when I showed the photo to the guy there of records I was looking for he had a root around and came up with 3 rare Erkin Koray singles, one of which was Estarabim so I grabbed it bartering him down to 50TL (about £20). Worth it, one of the best Turkish tunes there is:
Deform- This is the next nearest shop, located in the Çucukcurma district, where all the antique shops and hipster cafes are (love a good hipster cafe). Deform doesn't disappoint, with a great selection of 45s and LPs. Plenty of Ersen 45s (not the one I was after sadly) priced around the 50TL mark. The shop is really nicely decorated and has a clean modern feel. Very Retro. Also I found a cat napping in the bargain bin outside. Cute
Aslihan Pasaji- From Deform you need to head down to Galatasaray School and check out the bustling Istikal Caddesi, a huge pedestrianised (ish) thoroughfare, where you need to find Aslihan Pasaji, a two-floor book market. The easiest way to find it is finding Cicek Pasaji on Istikal, a very pretty arcade with restaurants all the way down. Go down it and follow it down to the left. When you come out of it you'll see the entrance to Aslihan Pasaji right in front of you. In fact, the first shop is right there. You'll see Rare Turkish 45s in the window of this stall. Unfortunately the guy speaks no English whatsoever and wanted to charge 75-100TL for anything, even completely battered records, so I left him to it. Next, head up to the second floor where you'll find Murgu Muzik (aka Bengi's Shop) which has plenty of good stuff. There's a massive selection of 45s, but the rare ones you need to ask for and then they'll be brought out in a smaller, manageable pile. Picked up a Senay 'Gercek Nerde' here for 25TL. Fair Price
Akmar Pasaji- This is first and nearest place to head to from the Ferry port. Easy enough to find. There are a few vinyl sellers down here, but the one you want is Zihni Muzik. They have a wall of rare LPs but everything in this shop is catalogued, so it makes for the most painless digging experience in Istanbul. I quickly found a Baris Manco 45 in there that I was looking for and they sifted it out for me fairly quickly. 40TL, not the best price for it but nevermind. They also had this for 80TL (I didn't grab it though), one of THE great Turkish dancefloor tunes:
Zoltan Records- Further down the same street as Rainbow 45 (if you're coming out of that shop turn right), but sadly Zoltan wasn't there and hadn't been for over a week... hope he's okay! It's supposed to be a great place for Turkish music so check it out.
Vintage Records- The last of the shops in Kadikoy was a disappointment. When I walked in I was greeted with a chilly reception by the 3 people in there, looking at me like "erm, what are you doing here". The guy was helpful enough, they have rare 45s organised appropriately, but the vibe was definitely "I hate the fact that you, a tourist, are coming here to rape my country of it's records". Fair enough really- Still, picked up a Disco Fasil Vol. 1 (it has a break on it) for 15TL so I left happy.
One final mention must go to a couple of sellers on eBay who can hook it up if you get in touch with them before you go. They are both based in Istanbul. Special mention must go to turkish_record aka Mustafa. I chanced upon Uc Hur El 'Gonul Sabreyle Sabreyle' for a BIN £20 whilst I was there (I know, browsing eBay on holiday, sad) and so I got in touch and asked if I could collect it. He also sold me Mogollar 'Cigrik' for £20 too which really is a fantastic price. Copies with the picture sleeve can reach the $100 mark so I was pleased with that. Also there's vintagemoviesandposters but his prices are a bit high. He wanted to sell me the same Mogollar (admittedly with picture sleeve) for £120, which is like $200, so, umm, yeah I left it
Ok, that's your lot, hope it's of some use to anyone out there digging for Turkish Delights!
*UK label Finders Keepers have done FANTASTIC compilations of the best songs from Selda and Ersen, they are well worth owning