Package 4 is the only package imported to Puerto Rico, so that's the one I have. I would've liked to have the side and curtain airbags (I had them in my VW Golf), but this is unfortunately not standard equipment in the Prius.
This package includes the rear wiper, the smart entry system, theft protection, and the Homelink mirror.
As I am in the automotive industry, I might be able to give an answer on side airbags as an aftermarket option.
From my research into this for some of my customers, there is no one that can do it for a few reasons. The biggest is safety. They would have to have many permits and licenses to perform that kind of work as well as certifications on their techs. The second is cost. You would have to tear out and replace so many different parts to do this properly, that it would not be cost effective.