i have a 2' deep cabinet that a district carpenter fitted with masonite
dividers for me. the slots are about 3.5" wide x 18" high they hold a
portfolio of poster board folded in half.
in a different building i had a large wooden bin on casters that was
made by someone long ago. if you don't have carpenters employed by your
district, perhaps you have a shop class or teacher who could do the
work, or a vo/tech center.
linda in michigan