Taisho-en is a working nursery in Shizuoka (the foot of Mt. Fuji). It is run by Mr. Nobuichi Urushibata and specialises in Shohin bonsai. That being said there were numerous examples of fine medium and large bonsai as well.
Mr. Urushibata offers 3 month student positions that can be arranged via THIS website.
*click images to enlarge