In Melbourne, Australia there were stores like that in pretty much every shopping center and they would just have all the usual colours and you would buy the ones your school wanted you to.
They would have different fabrics at different price points. We all looked the same from afar but there were differences up close.
I find it interesting that there weren’t any sets with the school logo at your school. My school used these to raise a bit of money and would buy them back and sell them second-hand as well when you were done.