I found this post on PingMag, a favorite Japanese blog:http://pingmag.jp/2008/07/03/water-balloon/ that no longer exists unfortunately. They visited Ito Rubber Balloon Factory in Chiba, Japan to watch this family run business hand make balloons. I have forever been in search of handmade balloons and have only found a business in Italy that still makes them. The colors and shapes are always better when handmade, and they often are biodegradable!
here is the post: