Is the counterfeit issue specific to the US, I have never had or heard of a counterfeit issue with Amazon UK?
It now takes less time to hunt down a reliable specialist online supplier, e.g., [1] than it does to wade through all the fraudulent listings and fake reviews on Amazon to find even a plausibly reliable product/vendor.
At this point, despite being a 20+year loyal Amazon Prime customer, I'm finding It's a better use of my time to find a good vendor, often family owned.
[1] I currently use batteryjunction.com, seems reliable, in my region for quicker shipping, no connection other than customer, and there seemed to be others of similar good quality in other regions.
Does seem like a big opportunity too! Ofc, need financing for inventory, but maybe partner with an existing supplier...?