Thank you for shining a light on this. Unfortunately, this has been a long struggle, which seems to have gone backward rather than forward in my lifetime.
My Grandmother was one of the original activists in the International Ladies Garment Workers Union (ILGWU) in the U.S., and later a union officer. Through blood, sweat and tears (literally), they were able to achieve some improvements through union contracts.
As a lawyer, I represented the ILGWU, and later UNITE, which was the ILGWU merged with the Amalgamated Textile Workers Union. But in my time, I saw the union shops close up one by one, until there were none left in Los Angeles. I spent more time in bankruptcy court than regular court.
Now, the work has shifted to local sweatshops, and even worse sweatshops overseas, such as where you worked.
I still ask for the union label when shopping for my clothes, which befuddles the salespersons who ask "How can I help you?" They can't. In Men's clothes, there are still a few suits and formal wear with the union label (mostly Teamsters, made in Canada). I've never seen women's clothes with a union label, except some gems in thrift stores.
But, you can still check for a FAIR TRADE certification. It is hard to find, but not as hard as a union label. I urge you to make sure there is a Fair Trade Certification on your line of clothes, so that those of us with a conscience can identify it.