I know Conklin:
And RK:
Make em, but you'll find almost all custom luthiers have them as an option, Novak used to basically screw the entire luthier world around by claiming they had a patent on them when they technically didn't really. There are also huge ergonomic benfits to having a fanned fretted guitar/bass.
I would like to one day own a .Strandberg* but as I don't earn the kinda money required to do so I'm thinking of building a guitar that'll steal from the design philosophies of all my favourite luthiers, fanned frets will be one of these stolen aspects as I truly believe they are the best compromise when you start using ERGs.