Micro SIM card for Samsung S3?

Was wondering if any of the Cellular booth is providing micro sim card for S3? And can i continue to use S3, and just to change the sim card to japan Sim so that i can use the internet? Or rather, a data sim card for sale instead of renting it?

Really need help on this, thanks.

This might help hopefully.
http://www.bmobile.ne.jp/english/

I'm renting a mifi instead since I need to use a few devices, but this looks like pretty good price.

We�fre travelling to Japan in Oct. I�fm still confused re phone options. All I want to do is data browsing (Hyperdia) and SMS use, no voice or email. What is my best option? Can someone help me clarify what�fs easiest option. The bmobile site is VERY confusing.

Here is another site to try.
http://www.econnectjapan.com/

Their site is a little easier to understand. To me it seems that bmobile is better deal for just a single user on a single device, but eConnect is better if you want to share and split the cost.