The Special Collections reading room at the Jewish Theological Seminary
usually has a few books on display. At the moment, several copies of Sefer ha-Zohar are being showcased. The two first printings - Mantua and Cremona - are there, and now I know why one was called 'ha-Gadol'.
A Zohar manuscript (JTS ms. 1614, ENA 991) is also on display.
Ronit Meroz has been leading a research project to study the manuscripts of the Zohar. For the proceedings of a recent conference on the Zohar, see here
. English summaries of the articles online!