although certain modifications to your new vehicle may not be "factory", there are ways to have them installed in your vehicle before you purchase it, and even have it built in to the price. dealers also tend to get better prices on such items then just the normal after market costumer.
i found such a team that installs after market equipment (although a bit late seeing as i have had my hch for a few months now). from what i've researched you can get quite a bit added to you vehicle and your dealer will be more then helpful.
for my sun roof i went through
classic soft trim. very knowledgeable and helpful. (shameless plugging, but hey; they did a great job!)
many varied
locations for those of us who are spread about the usa.