I don't know any person who could provide it directly. But I think here http://www.whoi.edu/redtide/research/projects you could find information. Also I would check for a research group directly at www.whoi.edu
I am almost 90% sure that you could find a researcher at this institute. I was working there for 9 month but in a Microbiology (Bacteria) Laboratory.
Try reaching out to the University of Tasmania, Australia. All of my research into it kept coming up with this school.
There were papers saying that ATCC would be expanding its protozoan collection to include N. scintillans for available shipping. However, the ATCC site did not have them as of yet.
We no longer have it in culture after Hurricane Harvey and I tried to isolate it earlier this year; however, I never found any in the samples I collected. I will see if we have some in our local waters now that it is getting cooler.