Have you considered a white amakusa? Grit range is said to be 700-1K on the Japanese scale, I feel that mine is in the 1K-1200 range. I don't recommend the amakusa red for anything but coarse work like removing chips.

I ordered mine years ago from here:
Amakusa White Natural Medium Stone, Medium Grit Stones

Found it cheaper here, should be the same stone:
BladeConnection: Practical and Tactical Knives for Daily Carry
Scott