Price of this puts me off as trying to do this at low cost.
Basically any clay should be ok, although avoid bentonite as it’s extremely small particle size leads to high shrinkage that you don’t want. If you are using it as a castable then it will be ok, but if for a mortar you might need to sieve the stuff to exclude any large particles. The homebrew has proved time and again to be superior to refractory cement for oven service conditions. It is also far cheaper. The powdered clay you’ve found sounds ok. Another source is pottery or ceramics suppliers