Staples offers the Jansport Vector Accessory Pouch in Black for $6.39. Opt for in-store pickup to avoid the $9.95 shipping charge. That's the lowest price we could find by $10. It measures 3" x 7.5" x 2.5".
REI offers its REI Men's Bolongo Board Shorts in Black or Midnight Blue for $23.83. Opt for in-store pickup to dodge the $5.99 shipping charge. That's $26 off list and the lowest total price we could find. They're available in sizes L or XL, although not in all size/color combinations.