Hangzhou is rich in silk, so the quality of silk here is better and there are many special varieties. If the budget is sufficient, I think it is a very good choice to buy silk in a specialty store. Of course, you will see many different stores in Hangzhou, large and small, and not every store sells more reliable silk. Keshi Ya is highly recommended. This brand of silk has been given to the wives of heads of state, so there is no need to worry about quality and reputation. If you want to choose other brands, it is recommended to choose brands with high-grade silk logo. This logo can't be hung by any brand. There are not many brands that can be hung, and the quality has been tested, so you can buy with confidence.
Going to a reliable store to buy silk, although it is safe to buy, seems to be less fun. So I recommend two more places, Silk City and Silk Street in Hangzhou. Xiushui Street has a long history and can be regarded as a place with a sense of history. They all sell silk, which is cheap, expensive, simple and complicated. You should find all kinds you want here. However, if you buy it here, you'd better have a certain ability to distinguish silk, because there are merchants who fool people with fakes, and you can enjoy the fun of scouring goods here.
These are the reliable places I recommend to buy silk in Hangzhou. I hope it helps you.