It's M&M Apparel and they are on Welsh just north of the CSISD Administration complex. They renovated a couple of years ago, and it is great. Parking is easy and they have plenty from the four big high schools plus lots of A&M. I liked that they had some all cotton t-shirts, sweatshirts instead of just the dry-tech material.
The Cougar trailer also has a lot of items, and they usually advertise on the social media accounts so look for that too.
Start your school year off with spirit!