Making a quantity Matrix for wholesale website

I have a wordpress theme that im using to make a website for screen printing company. They have multiple wholesale accounts and want to show every single item of clothing that they can get for customers. Which a lot of clothing ?? But the problem I’ve run into is making an quantity matrix for customers to choose multiple quantities of shirts sizes and colors at the same time and have it add to the cart. I want it to work like this:

https://saltcityprinting.com/wp-content/uploads/2012/02/Screen-Shot-2012-02-06-at-12.35.04-PM.png

Then just have a add to cart button underneath integrated with cart66.
what’s the easiest solution to doing this? And is there a wordpress plugin out there that does something similar? Any help will be much appreciated!