I found a chrome extension (AMZScout Stock Stats) that gives you the exact stock volume for a product on Amazon.
I found a website (Sellics) that tracks your competitors exact daily sales but it is not free.
If these tools can do that so there must be a way for me to perform that.

So, how can I track competitors daily sales/stock volume by myself without using another tool?
I know that I can put an item in the cart and try buying 999 items to see the stock level, but I need an automatic process to do that.
Maybe can I do that by creating a python scraper?

Maybe can I do that by creating a chrome extension?

Or can I do that by MWS o associates amazon API? I searched for this option but I was not able to find a solution.

Thanks