They sell it home depot and lowes too. It's a course soil with good aeration and fast draining, it dries out pretty quick. I live in SoCal so easy to find, we got cactus everywhere. I know alotta peeps shy away from miracle gro but they make some, as well as, there is cactus/ succulent mix too, made by different company.Agemon if you do not mind me asking what is cactus soil.
I believe Uni Gro is the company that makes the one I use. I'd post a link but I get my hand slapped when I do that...
You can also look on The Zon.