[iteachrfuture]

I am having the same trouble. This is what I figured out so far:

I definitely want plastic. Cardboard breaks down too easily.
Lakeshore has them for $4.50 but free shipping over a certain amount.
Really Good Stuff has them for as low as $3.33 each-but no free shipping.

I'd like to invest in something I can use multiple years. Like the other post, I was considering ice boxes. I heard the dollar stores sometimes have magazine file holders. I have also heard Target should have them for about $2 each.

I am still searching for these as well. If I find something for less money than $3 each-I'll let you know!