Sorry to revive an old thread, but I found a dealer of the knives in San Diego and included the link in my videos. It's called a Masahiro 240mm Fish Filet Knife. They have a single and double bevel knife.
***THE BEST*** How to Fillet a Fish (Mahi Mahi for Sushi) / How to Clean a Fish - YouTube
***THE BEST*** How to Fillet a Fish (Yellowfin Tuna for Sushi) / How to Clean a Fish - YouTube