Unfortunately, there are no extensions available for Viale model.
However, please consider the following solution:
Many of our customers in situation like yours are coming up with building a soffit box to lower the ceiling at the place where the range hood is supposed to be installed.
This is a simple frame made of 2x4's, covered with Sheetrock and painted to match the ceiling. It will cost you much less than any island extension on a market.
You can build it any size and shape you want. Plus you can get really creative and add some lights to it, giving additional illumination to your hood, or LED light strips facing the ceiling. So it will look very beautiful and elegant, like it meant to be there.