We recently returned from a Cruise that had stops in Ephesus and Istanbul. I reached out to the recommended Rick Steves tour company, SRS Travel, for assistance with some independent tours of these cities. The communications with the team at SRS was flawless. The guides we got for both Ephesus and Istanbul went above and beyond. Our guide in Ephesus was Ms. Jay Baydur. She was very knowledgable and experienced and allowed us time to explore the sites at our pace. My husband is a photographer and she would point out various advantage points for his pictures. On the return to the ship she made a reservation at a nearby restaurant for a true Turkish meal....which was delicious. She also shared the best place for Turkish Delights.
I don't recall our guides name in Istanbul but he too was excellent. He showed us how to use the public transportation, how to get the Istanbul card, restaurant suggestions for further adventures in the Asia side of Istanbul and how to get there on the Ferries. His explanations were clear and he too was very knowledgable. He was patient with my husband's photography stops and helped point out various advantage points. His restaurant suggestion was also delicious. After going through the Spice Market he took us to a specific dealer outside of the market for the better spices.
Don't hesitate to reach out to SRS Travel via email, to arrange your guides in Turkey.