Amazon.com: BOX USA Moving Boxes, Extra Large 20" x 20" x 15" (12 Pack), Corrugated Cardboard Box for Packing Packaging Storage Mailing, and Shipping for Office of Home, 32 ECT - Pack
Lowe's 24-in W x 18-in H x 18-in D Classic Large Cardboard Moving Box with Handle Holes in the Moving Boxes department at Lowes.com
Large Cardboard Boxes | Bulk Moving Boxes - uBoxes.com