Are you looking for a bag or a truckload? Call a landscape supply company (up in Sonoma County where I am there are quite a few) and ask them. You can even go to the yard and see the material yourself. Many will let you fill 5 gallon buckets if you only want a little, or deliver you 20 yards if you want a lot.

@Sara Malone Zone 9b I think half a ton would keep me going for a while. I have looked at some of the better-known supply companies, but the problem has always been that they have the "fines" included. Typically these are base rock products.

I found one candidate with a good photo. The problem with these landscape supply companies is that they have no datasheets for the products they sell, so I have no particle analysis. The #2 Olympia Sand on the linked page is the only sand I could find out of 10 landscape suppliers that visually looks close to what I need. Do you think this is horticultural sand?

I don't know...I would at the very least call them and discuss it with them, but even better, go to the yard and look at the material yourself.