Given the mention early in SoS of an auto-tailor that produced Utena's uniform at WPI, I suspect most people's clothes in cities like New Avalon are tailored.

For example, you might go through the racks to pick out something you like the look on, but it's not "do they have this in my size" it's going into a booth that takes your measure and the design of the item that you want and they run up a version cut specifically to fit you perfectly.

So it is perfectly ordinary T-shirt and jeans... but by the standards of the 23rd/24th century which are much better than our 'off the rack' would be.