Many places to purchase covers for an iPad with a quick Google search or at an Apple Store. Personally the one I like the best are the covers from Apple. The
Smart Case in particular. I realize you want cheap, but this case is worth every penny. It has multiple purposes which is what makes it such a nice case. It can be used as a stand, it wakes the iPad up when you open the cover, It is also a thicker case which will offer the ultimate protection for the iPad. I have a couple iPad's in my home and all are in this case since new. All the iPad's still look new because of the cases.