I have found a few ppl here in okinawa who sell them privately.
The problem is, none of them know how to take care of them...one lady was feeding them cat food.
Anyway, doubt you will be able to bring them, there are strict rules about exporting/importing domestic animals muchless exotic.
I'm all about stretching the laws and rules to the limit, but this is one that even I doubt I could pull off...if you get what I mean.
I was just talking with my wife and she knows of someone bringing a pet turtle...so it might be possible.
The for sure way to know is by contacting someone from this site:http://www.usarj.army.mil/organization/vet/index.aspx
Someone above mentioned a 16 hour flight.
If you fly AMC, the rules are a little different. You most likely won't fly straight through. Typically you will fly to your port call, like ours was in Seattle. The overnight before taking the AMC flight the next day. You also don't have to go through all the crazy customs stuff you'd have to if you go commercial. Which makes it much easier to get pets in and out of Japan. My wife's friend actually carried her small dog into the cabin on the AMC flight.
Anyway, I hope you find a way. Good Luck!