Amazon.com: 3/8-16 x 1-1/2" Carriage Bolts and Nuts Kit, Round Head Square Neck Screws, Stainless Steel 18-8 (304), 10 Sets : Industrial & Scientific
Amazon.com: Hillman Group Galvanized Carriage Bolt 1/2” x 16”, 25 Count, Blunt Point, Alloy Steel, Self-Locking Round Head Fasteners, for Wood and Metal, No Washer Needed, Rust-Resistant (812642) : Industrial & Scientific
Amazon.com: Stainless Steel Sign Mounting Hardware Carriage Bolt with Security Nuts Kit 5/16"-18 x 2" for U Channel Post - 48 Pieces : Industrial & Scientific