Where to shop Japanese designers for adults

Hello, I'm from NYC and will visit Tokyo in two days. I would like to shop for some authentic Japanese designers for women 30-50 years old. I know there are many dept buildings and area for cheep teenagers and much younger women. Where is the area I can shop for mature women by cool Japanese designers? I know where Yohji, Issey Miyaki's stores are, I'm looking for other Jap designers' stores. Thanks for your help!

Isetan Shinjuku

Depends on what type of designs you like. There would be many designers that aren't to your taste.

But realistically, the shops shouldn't be difficult to find. Even this website in the shopping section lists a lot of upmarket shopping areas where these high end shop would be.

As mentioned, you can still find them in department stores (in fact, department stores mainly sell clothes for mature women as opposed to those for teenager), but was Google not helpful?
http://www.isseymiyake.com/en/shops/store_locator.html#RETAIL/
http://www.yohjiyamamoto.co.jp/shopinfo/