Walmart offers the Black + Decker Corded 12-volt Pivot Car Vacuum for $38.51. Choose in-store pickup to drop that to $28.41. That's the lowest price we could find by $9, outside of the mention below. Its adapter fits cars' cigarette lighters. It features 10 settings, a crevice tool, and 16-foot cable.

A close price: Amazon charges $28.99 with free shipping.