Here is where I get my paper storage racks. They have tilted slots so it is easy to find what I am looking for and most are stackable so I keep adding on when I need it. I am so happy with the way it looks. I also added pegboard above my desk and use hooks and shelves to put all the other stuff on.

Note, shipping is costly but I have done a lot of research prior to purchasing and even with shipping these are by far the best prices for these types of products.