What is the name of this 3 open tube and where can I purchase one? I would like to do some plasma activated water tests. 

Does anyone know the name of this three open tube along with where I can purchase one?  

The screenshot came from this video if you need a better angle to look at it.  Here's the video, the screenshot came from
YouTube
The flask pictured in your question is simply a three necked round bottom flask. They're available commercially in a variety of sizes with different configurations of ground glass joints (personally, I've always found it easier to buy single neck round bottom flasks and then get our glass blower to append the joints where I want/need them).