If you want a diamond sharpener nothing I'm aware of can even approach the quality of Japanese Atoma plates. They're very expensive but you can get a small slice made for Edge Pro use for a lot less. These 1" x 6" strips are mounted to EP blanks but are also perfect for portable use freehand.
_________________________
“I'd rather have questions that cannot be answered than answers that can't be questioned.” —Richard Feynman