@HeatherR - To expand on the post from my friend
@sorce , Napa 8822 is fossilized diatomaceous earth. It is a stone that is almost entirely silica, meaning chemically inert, and has a very fine pore structure to its particles. My caution is that the particle size of Napa 8822 is too fine to mix with Akadama or Kanuma. The Napa product is available from auto parts stores. But I do not use it as its particle size is too small. I have not been able to find a source for a larger particle fossilized diatomaceous earth.
A better mix is to use pumice, pumice with Akadama, or pumice with Kanuma. You can use both the Japanese products "straight up", though for various reasons most of us use mixes or blends of several components. I like 100% Kanuma for my azalea. I use mixes for everything else.
Potting mixes tend to be very individual. I highly recommend using a sieve to remove fines from your potting mix. Anything that goes through a piece of window screen is too fine to use for bonsai or any houseplant in a flower pot.
Many, many different soil mixes will work if you can water them correctly. I like a mix that lets me get away with watering every third day. This allows me a long weekend for travel without having to hire someone to come water my trees. Most exhibition bonsai are potted in mixes that require daily watering. This means a team of people are required to keep the tree properly watered.
I don't want to make the topic of potting media too complicated, but it is the most technical aspect of bonsai horticulture. And it is an aspect of bonsai horticulture that is continually evolving. Products that are available today are nothing at all like what was used 40 years ago. There is a constant evolution of this aspect of the hobby.