If you are flying domestically, the airlines here have cases you can reserve for your flight. They are simple cases, but they handle them impeccably and I've not had, or even heard of, any damage in 10 years as a professional bassist in Japan. I never worry on domestic flights, and that's saying something.
If you are flying internationally you'll need a case like the Stevenson, Gage or Kolstien. I'm personally partial to the Stevenson. You should talk to Yamamoto bass shop
http://www.yamamoto-bass.com/index.html or Takasaki
http://www.contrabass.co.jp/ both of which have cases available for loan/rent if you're returning. If you want a case because you're (for example) returning to your home country, you might get lucky and be able to buy one, I'm not sure.
Although like I said I'm partial to the Stevenson, the Gage case Jon linked to looks like a good deal, as well. But do look at the shops I mentioned.
Where are you located? If you're outside of Kanto and can't get to Tokyo, I guess that could be a problem too.
Brent
