Mysterious does say it's in Tribeca now-- I haven't been there since their move from the midtown place with the spiral staircase and Penzler's back room full of rarities that he'd let select Sherlockians glimpse during the SH Weekend in January. I'm sure he still has loads of Sherlockian books and items.

http://www.mysteriousbookshop.com/pages/about-us