Pop Space (which is affiliated with Few Many), is located on the first floor of the Marui One building (the same building where Kaiju Blue used to be). It's pretty easy to find. First, the details:
Store address: Shinzan Bldg 1F, 3-17-21, Shinjuku, Shinjuku-ku, Tokyo 160-0022
〒１６０－００２２ 東京都新宿区新宿３－１７－２１ 新三ビル１Ｆ
Phone number + Fax: ０３ー３３５３ー２５３２
Hours: 12 PM - 8 PM (open every day)
I haven't had a chance to add it to the Kaiju Korner Tokyo Toy shops map yet. For now, click here for a map to the exact location.
More store pics: