If you would like to wait for a little while, some of the Freestyle goods will be sold online via a mobile site in Japan as if mid-March, is only available to Jweb members, but I-TM4U has a membership.
For the present time Johnny's has goods from all their idols for sale in official shops (one just down the street from the I-TM4U offices) but, they work along the same lines as the exhibition, where you need tickets to get in, so any purchases made in stores would have a standing fee attached. There are also limits on how many goods you can buy.
However, Johnny's also sells idol goods by mail order catalog in Japan, and I-TM4U is going to work on making these items available to overseas buyers, for the same price as a Japanese customer, with a small service fee attached, they are JE fans too! At some point Johnny's has plans of making the mail-order merch into an online shop, we will keep you up to date.
Thank you for your patience!