Amazon has 6.5″ DeWALT 40-Tooth Circular Saw Blade (DWA161240) for $11.98. Shipping is free w/ Prime or on $35+ orders.

Features:

• Made from high-density tungsten Carbide for toughness, wear-resistance, and long life
• Tough coat anti-stick coating reduces friction and gumming
• Thin kerf design for smooth cuts
• Reinforced shoulder for impact resistance in nail-embedded wood
• Optimized for use on both corded and cordless circular saws