These lava lamps are inexpensive but very good。 Typically they sell around $20 a unit. It takes a bit long (sometimes 3 hours) to heat up, but once it is heated up, it changes colors as well. Perfect for kid's room. 可以用作装饰灯。
You can find them at Amazon.com, they have many different colors and the size, such as these classic lava lamps
Here are some more useful information about lava lamps:
During initial warm up of your Lava lamp, the coil in the globe may tend to stand on end or float to the top of the globe. If this happens, keep your Lava Brand Motion Lamp operating for 4 hours or more to allow the "LAVA" to become completely melted. The coil should then automatically drop to its correct position at the bottom of the globe. If the coil does not drop down, twirl the globe gently in the base and the coil will drop.
Don't Move or Shake your Lava Lamp while the lava blobs are "WARM"! This will cause your Lava Lamp to become cloudy and will most likely permanently malfunction!