After I ordered it, I sent a mail
"May I get it at the shop in Akihabara?"
They replied the next day.
"What?"
The adress of the shop was in the mail. It was in Saitama Pref. ...
I was convinced that it was the "junk-shop in Akihabara" where I had often gone.
I succeed to change the battery cell and there remained the plastic shell and voltage controller for 3 Li-ion cells.