As noted in the January 6 update to
Bill's Blog, a standard linoleum tile floor is a very good approximation of the "Regolith" flooring material. During development, we found that a waxed floor game performance characteristics that were within about 5% of the official material. That seems to be good enough for most development efforts, and should make for a very reasonable alternative for teams that don't want to purchase enough of the plastic material for an entire floor.
-dave
.