OXA USA via Amazon offers its OXA Ultrasonic 4-Liter Cool Mist Humidifier in Gray for $39.99. Coupon code "JGWSYDAI" cuts that to $27.99. With free shipping, that's $12 off and the best price we could find. It features up to 16 hours of continuous operation, dial control, and auto shut-off. Deal ends July 31.