I've spoted this lapping plate fist on youtube. I contacted my supplier in Japan, and he found this lapping plate for me. The name of this product is Mensuri.

They were manufacturing 2 sizes, 262x115x15mm and 330x130x30mm. However the larger size was discontinued. Since my stone collection growing and growing, and I am using stones for razors and Japanese knifes as well, I am sure I need one.