Howdy,
I did not know and my single Forschner blade has a rosewood handle rather than Fibrox, but I got interested in the question and did a little digging. I still don't know for sure, but I have an educated guess for you.
The Victorinox web site does not identify what fibrox is, but there are a couple of web sites for cooks that promote the Fibrox line because they say the "Nylon handles are more hygenic". So I'm guessing that they are using some form of FRN, Fiber Reinforced Nylon. There are numerous grades of FRN with different grades of nylon and different loadings of glass fibers. (I doubt that it is the same grade that Spyderco uses for its Native line. From examining closeups of Fibrox handles on the Vic website, I'd guess Fibrox nylon has a lower molecular weight and a lower glass loading than what Spyderco would use for the Native, so the Fibrox won't feel the same.)
If that is the case, you will not be able to buy it because it has to be formed under extreme heat and pressure. Having slabs won't do you much good. Oh, and the reason no one sells "Fibrox" is likely that Victorinox is the only one who uses that name for the material.
my best guess.
Frank R
