Oak Leaf via Amazon offers the Oak Leaf 140ml Color-Changing Aromatherapy Essential Oil Diffuser in Bamboo for $19.99. Coupon code "4YXV7YCR" drops it to $16.99. Plus, Prime members receive free shipping. That's a $1 drop from our May mention, $53 off list, and the lowest price we've seen. It features a 7-color LED light and auto-shutoff.