Prazi PR-2700 Beam Cutter for 7-1/4" Circular Saws — Toolbarn.com
Harbor Freight Turns Your Circular Saw into a Beam Cutter for $60
Amazon.com: Prazi USA PR2700 Beam Cutter, Circular Saw Blade and Chain Attachment, Increase Cutting Power and Capacity, Fits most 7.25-inch saws : Everything Else