Sears offers the Craftsman Hex to Square Socket Adapters, model no. 26352, for $1.49. Choose in-store pickup to avoid the $5.99 shipping fee. That's tied with last month's mention and the lowest price we could find by $5. It purports to fit all brands.
Of note, Shop Your Way Rewards members will earn a Sears credit with this purchase and may be eligible for additional credits and discounts.