flat lids from plastic tubs (Terra Linda - San Rafael)

I am looking for a number of flat plastic container lids for an art project. I can cut the latching edges off, but I need the rest of the surface to be flat and smooth (I can remove labels) ... no curvature or texture, raised logos, etc. A great example are the bins Safeway Organics salad greens used to come in before they were shrinkflated down from 1 lb. (with an increased price) and given a plastic film top. I need rigid plastic, not film.