I've found all ingredients to Howard's potting soil mix as listed in th BOP, but can not find decomposed granite sand. Wells Bros. had it in bulk, but couldn't use that much.

I've looked in East Plano area and Murphy, TX.

If it is not available in bags, what should I substitute?

I can't find it either. If anyone can help I (we) would appreciate it.

I called Living Earth Technologies and asked if they would sell a pound, and they said yes. I called the location off Northwest Highway. You will need to bring your own container to put it in. I do suggest calling ahead to double check. Although I have never experienced this with Living Earth Technologies, I have found many times in many places that sometimes it depends on who is working or who you speak with as to what answer you are given.