Got lost on my way to my friend’s home, near Prince Edward MTR, towards the Northwest into Sham Shui Po. In return, I found these few streets, close to the Poplar Street market, around Maple & Tai Nan, where most of the shops (if not all of them) were selling fabric, garment, textile, whoever you like to call it. Here is an approximate, non-exhaustive map:
View Garment Street, Sham Shui Po in a larger map