Its Canadian, Northern Arm makes a nice one. Either 6" or 9" made in magnacut. I have the 6" its pretty sweet
White River Knife and Tool makes a step-up filet knife in S35v. Haven't used the filet but do have some of their other knives and love them.
I have the 6" and it is every bit as flexible as any fillet knife out there. I haven't used it much yet, but I suspect it will be top notch for silver skin. I also picked up a meatcrafter to use along with my vics.
I am tired of knives dulling out breaking down animals so I thought I'd try out...