I'm just adding the shaders to the jar (with no package, but that should work as well) and get the stream to them via
this.getClass().getResourceAsStream(name)
However, some tools for deploying the app via USB seem not to support this way. They simply drop all non-class files from the jar when creating the APK, because the behaviour of what is supposed to happen to these files isn't very well defined for Android/Dalvik.