Housmile via Amazon offers its Housmile Pure Essential Oil Waterless USB Portable Aromatherapy Diffuser for $29.99. Coupon code "XQ35FTZP" cuts it to $14.99. With free shipping, that's the lowest price we could find by $20. This mini aroma nebulizer measures 2.7" x 2.7" x 4.9", covers areas up to 215 square feet, and charges via USB.