Mhpgirl via eBay offers the Goodyear Super Dry Natural Drying Ball 2-Pack for $1.50 plus $3.46 for shipping. That's the lowest total price we could find by $1. They each measure 4" x 2" and are made from non-scratching natural materials.
Walmart offers the Stanley 16-Piece Passthru Set, model no. STMT74900, for $19.97. Opt for in-store pickup to avoid the $5.99 shipping charge. That's $10 off and the lowest price we could find, although it was $5 less in September. It features chrome vanadium steel.