I guess in the United States Amazon is a good choice for these items.
As I'm from Mexico* usually I order these japanese figures from stores like AmiAmi, HLJ (in these stores they have great discounts especially AmiAmi) or Nippon-Yasan (if it is a exclusive item) when Tamashii Nations warn that they will open the pre-orders at a certain date.
*In my case I get cheaper express delivery from Japan that from the United States.
As is known the exact day of their release I'll alert here
New figure in this line: VF-1S Strike Valkyrie (Roy Focker) for April (this TWS exclusive includes a special edition of the Tamashii Stage Act. 5 until Nov. 4):