Jeremy:
Good luck finding the N. viridescens in the pet trade. I only found them once in a Michigan pet store about 10 years ago. However, they can be fairly common in the wild in southeastern Michigan. I commonly find efts in the springtime or fall under logs in the same counties that I mentioned in the other thread. However, as much of a caudate enthusiast and explorer that I am, I have never found an adult in the wild.
I believe that the next month or so would definitely be a good time to search for efts. If you are having a hard time finding areas to search for animals like this (and areas where it is not illegal to collect a couple), try state game areas (hunting lands). Of course I wouldnt go tramping around those areas during prime hunting seasons, but I have had a good amount of luck in places like those. Can't think of any spots off hand in your area though...