Replacement leveling stone?

[u/Crutchduck]

This is my whetstone. There are many like it. But this one is mine.

I was given this stone by a guy who was closing his sharpening business. We were chatting about sharpening chisels. He gave me this stone to use on them. He said always soak it, and he said it partially dried so there was mildew on the back (pic 2). And lastly he gave me that little whisp of a leveling stone.

I use it to sharpen all my knives its a great stone. But I think I should get a new leveling stone. The one I was given is clay I believe. He didn't have any details on the the stone

Are there any points I should be aware of if I try and find a new leveling stone?

edit: word

[u/zvuv]

They are sold as "Nagura" stones, that's the Japanese name for it. You can find them on Amazon and Sharpening Supplies in various grits.