part replacement for fuel regulator 1999 b2500 mazda

I would consult your local Mazda dealer for further information. I don't see why it would not be available. Also, you can check a Ford dealership for a 1999 Ford Ranger with a 2.5L 4 cylinder engine -- same part. However: why are you looking to replace it? Not a common failure.

The fuel pressure regulator is part of the fuel pump module assembly and mounted in the fuel tank on the side of the assembly. more than likely you will have to purchase the Module Assembly to get one (IF that's the problem),don't think it's sold separately.