By the way. I wanted to buy some of AR t-shirts but they are all made of cotton.

Why not using some quality synthetic fabric like used for sports' t-shirts?
Synthetic are the best. Quick drying and "breahable".

Cotton is the worst fabric that can be used for clothing. "Breathes" poorly and traps sweat and/or water making it difficult to dry. It's awful to wear during hot weather or when doing sports/workout.

Unfortuntanately, it is ridiculously cheap so almost every "designed t-shirt" seller uses it :-S
If you had some synthetic fabric as alternative, I would buy loads of them.