Hi, Meee1111, there is several Kebaya online store in Indonesia but to be honest, I don't know which one trustworthy enough to buy from because usually I never bought Kebaya online. There are several things about Kebaya which need to be feels and touch first to know whether it is good and pleasant to wear in our body or not mostly for sensitive skin like mine. But if you search for "Kebaya" in Facebook, you will find several online stores there, but most of it in Indonesian language.
If I may suggesting you, try http://www.anneavantie.com and ask them how to buy their Kebaya online. They know better than I do. :)
I'm so sorry I can't do much help for you.
Have a nice day.