O-Z Gedney 4" 2-1/8" Deep Octagon Box at Main Electric Supply
RACO 3-1/2" Galvanized Steel Octagon Electrical Box at Menards®
Steel Octagon Boxes and Covers | Crouse-Hinds series | Eaton
2 Pcs, 4 In. Octagon Box for Cut In Old Work, 1-1/2 In. Deep, (2) 1/2 In. Side Knockouts; (3) 1/2 In. & (2) 3/4 In. Bottom Knockouts, (4) Threaded Mounting Tabs, .0625 Galvanized Steel - Walmart.com