I have a NeuroTrek. There is a new version out I believe. Google "Neurotrek 3".
Yes, if you are going to experiment with hemisphere isolation, I would go with the left. Though I don't fully understand that process. How does that implementation keep a balance of voltage from left to right. Without a balanced voltage application there is the possibility of electrolysis of the blood (I think that's the term, has to do with component separation).
BTW, I would not do the 20+ CES followed by 39.5 Hz audio. That is not what I suggested.
Your best bet is to drop the bucks on a Neurotrek.