It’s not much of a “quarter” but this map suggests there’s a few stores between the 5th and 11th wards, with more a little bit scattered around. This listing suggests there’s a few to be found in a block between 50th and 50th lower street, around Sule Pagoda, as far west as Bo Ywe Road.
Very few of these actually have websites (though some list a phone number), and a lot of them seem catered to cellphone accessories, but that should hopefully give you a place to start and narrow it down.
Credit:stackoverflow.com‘