National Hardware 5/16-in x 5-in Zinc-plated Interior/Exterior Coarse Thread Eye Bolt in the Specialty Bolts department at

Pro Shop - Fasteners - Bolts

Square U Bolt - Zinc Plated N222-372

Screw Eyes - Metal Hooks - The Home Depot

Fasteners McGuckin Hardware

Hillman 3/8-in X 3-3/4-in Zinc-plated Coarse Thread Bolt, 59% OFF

Pro Shop - Fasteners - Bolts

Hook & Eyes, U-Bolts, Turnbuckle - Hardware - Knudson Lumber

Eye Bolt - Storm Shine N820-086

Square U Bolt - Zinc Plated N222-372

3/8 in.-16 x 5 in. Black Exterior Carriage Bolts (25-Pack) 261287 - The Home Depot

Eye Bolt, Zinc, 5/16 x 3-1/4 in.