rigid foam or styrofoam sheet (Shirley Center)

Got a 2'x4'x4" (approximate) box I need to fill with rigid foam or styrofoam/polystyrene insulation. Ideal would be half sheet (4x4) of 2" rigid foam, but I can play 3D tetris with flat pieces at least 1' each side. Don't need coolers or non-flat packing filler, do need enough to make worth a pickup near Shirley (so please describe!), just trying to keep stuff out of the landfills before buying more than I need at the big box store.