I shipped a pretty large one to my brother once. It cost less than a hundred dollars to ship, but I had to send it by ship so it took about six weeks, maybe longer to get to him. If you want to try reverse engineering one, I can take some pictures of the heating unit for you.

I started to look into the history of 'Girls and Boys Day' and it looks like the origins reach back about a thousand years. I've only skimmed some articles, and I can't understand some of the kanji being used, but it appears that this day has been celebrated on March 3 since about six hundred years ago, and dolls of one kind or another have been a part of this celebration since the very start. When I know the details better, I'll let you know.