Walmart offers the SOG Specialty Knives & Tools Key Knife in Black or Blue, model no. KEY-101, for $7.97. (
Amazon offers it in Black for the same price.) Opt for in-store pickup to avoid the $4.97 shipping charge. That's the lowest total price we could find by $7. It measures 4" overall (with closed length of 2.5") and features a 1.25" 420J2 steel blade with a drop point shape.