I occasionally find the fruit in the Oriental market but can't remember offhand what season they are available. If you have any ethnic markets nearby check them out.

These are in season in late August where I live (Florida) and only for a very short time. I also get mine at my local asian market.

I recommend flora exotica which is in canada shipping is about 25 us dollars but you need to be patient it takes a while until he ships the plants.
I bought Capulin Cherry or Jamacian cherry, Sugar apple, and Carambola or Star fruit from him and arrived in good condition.
Here goes the website
http://www.floraexotica.ca/Fruit.htm
Good Luck!