RTW = Ready To Wear. I.E. taken from the rack and put on.
Modern Tailor = makes Made To Measure shirts based on your measurements. They make them in China and ship them to pretty much any country, so even if you are from Syria, you are most likely going to be able to get MT's shirts.
Suit Supply = since you have this in your country, I would go there and try some of their shirts on. Most likely your best bet. Having SS in your country means you are from a developed part of the world and have access to pretty much anything you want to get your hands on.
Will go on Sunday/Monday and post back with the results! I've tried measuring myself, but according to what I got, I'm smaller than the extra small sized shirts at the sites I was linked to. That's odd, as I have wide firm shoulders, in fact a blazer I borrowed from a friend was way too tight for my shoulders, and it was "M" sized ~$150 blazer. It was also a bit too far from my stomach, the sleeves were alright.
Will post back with the results and see if I can get any pics of the shirt to get an opinion. I think I need at least 2 shirts for the beginning, can't go wearing the same clothes day-in-day-out.