I’m absolutely no expert about this but over the course of time and at looking at these cars, I’ve come to understand the process a little bit.
This is a good video showing the time and process involved in completely transforming a car.
Of course that doesn’t exactly answer where you would get the decals from, does it? (That would involve stuff like screen printing and other stuff I don’t know anything about)
This (http://www.itasha-guild.com/price/) is a company dedicated to itasha and offer various methods and stickers. That’s just to give you an idea of price, since I don’t think it would be practical if they shipped overseas. (I know there are other businesses like this and I’ll keep an eye out to post them when I come across them again in case they add any addition information)
HOWEVER I’m very sure similar (albeit not dedicated to such a particular type of business) are located throughout North America. I googled for my city that even being smaller than most, I was still able to find quite a few business that offered vehicle graphic services that would get this desired effect. Just keep it in mind it’s pretty pricy!
And I guess if you aren’t picky about images or possibly getting scammed or ending up with a bad product that falls off in a day, sellers on ebay and taobao sell decals that can work for your car. But again, the quality and legitimacy of this isn’t the best so I wouldn’t really recommend it?
Amiami occasionally has smaller stickers for your car that are legit and cheap but they’re few and far between. (http://slist.amiami.com/top/search/list?s_seriestitle=Ita+Goods)
These are just my opinion and ideas on the matter. Sorry if it wasn’t the most helpful information, everyone. If anybody who actually knows about this kind of stuff has anything to add, please do.