Monica Mattiolo
Monica Mattiolo thanked DDX Project's answer

http://www.uniqlo.com/us/women/tops/t-shirts.html

or

https://www.everlane.com/collections/womens-tees

Dirt cheap but adequate quality and good cotton. Especially the Supima cotton t-shirts.

But if just want t-shirts for wearing around the house then a pack of Kirkland T-shirts from Costco will serve you real well.