Personally, I would just buy old usgi mags.
I’ve had a bad experience with them and their 30 carbine mags.
JMO.
My experience with the KS mags has been pretty positive, but I bought them a long time ago.
The best mags I have ever seen are the Taiwanese mags that J&G Sales sold years ago. Cheap and better than any USGI mag on the market. Next to them are the Jahn mags that APEX occasionally has for sale.
I've had good luck with the Korean mags. I bought some of them in bulk a while back, and if/when they crap out, I can just replace them with another one from the pile.