Walmart offers the Stansport Traveler 36" Duffle Bag for $16.98. (Amazon charges the same.) Opt for in-store pickup to dodge the $5.99 shipping charge. That's the lowest price we could find by $4. It's made from 600-denier dacron material and has self-repairing zippers.

Update: It's now out of stock at Walmart; however, Amazon still offers it for $16.98 with free shipping for Prime members.