I have the same problem finding "Koa Fun" where I stay but I came across a recipe for making it at home.

First, you need to steam the regular glutinous rice flour for 10 minutes, then microwave it in 1 minute increments till it is slightly brown. Let it cool and use as directed in recipe.

I am planning to try this next week and try to make my first Snow Skin Mooncake. I will post the recipe if it works out well. Good luck.