But, for a mister, the easiest thing to do would be to get a small water pump from wherever, and get some tubing and misting nozzles. All these are available at either a Hydroponics shop or online. If you shop around, you could build the misting system for around $30. Remember to get a pressure rated pump, for fountains and such. You also want to make sure that wherever you reservoir is, the pump has enough head (vertical pumping height) to reach your terrarium.
And buy different micron size misting nozzles. You may find you want more of a fog, rather than mist, so getting a few different sizes to try would be a good idea.