Is this preferable to "fibrament" for a home oven?
John, it depends on the oven, and on your desired style. For those seeking faster New York bakes, and for ovens with broilers in the main compartment, which, if memory serves me correctly, is you, and is also the majority of ovens, cordierite is superior to Fibrament, as Barry pointed out. If the broiler is in a separate drawer, then Fibrament is the better choice.
As far as cordierite stones go, this is one of the better ones. Not counting the legs, I think this could be either 5/8" or 3/4". It also appears to be a quality cordierite.
If you are attempting to match this material exactly, that can be problematic. Cordierite can vary in both composition and manufacturing process. A new cordierite stone will most likely not have the same baking properties– at least, not exactly the same. There will be variations.
While there are some sources of cordierite that have confirmed higher conductivities (Mike (Essen1) uses one), if you are shopping for a hearth, as long as you have an oven that can reach 550 and have a broiler in the main compartment, 1/2" steel is a better candidate.