Groupon offers the Disney Star Wars R2D2 Ultrasonic Cool Mist 1-Gallon Humidifier for $49.99 with free shipping. (Amazon charges the same.) Outside the mention below, that's the lowest total price we could find by $4. It measures 8" x 8" x 12".

A close price: Woot has it for $45.99 plus $5 for shipping.