I have used South Coast Supply in Los Alamitos recently. I can tell you that 1/2 a yard is only $14.

Do you need it delivered, or can you pick up? Is outside Toronto (45 minutes west of the airport) close enough? We have a huge pile of well rotted sheep manure. The price is an appropriate donation to Cornshare which donates grain to 3rd world countries. We can't deliver.

Check with a local Farm Supply or Feed & Seed store. They should carry one or both or ask a local nursery to order the quanity you need. Some will include special orders with their regular stock orders. My supplier has both in 50 lb. bags, but only carries Aluminum sulfate in granular form. They sell only to the trade and have a hefty minimum purchase requirement. I haven't heard that Aluminum sulfate is consided an explosive. I believe that a permit would be required to purchase it, if that were true. Of course, many substances in powdered form(even flour) will explode if the right conditios are met. Rb

It might not be quite organic but you might look into getting some mushroom compost from montery mushroom farm. Could get a whole pickup truck load for less than a big bag of good potting soil. As a resident of Orange county you could also contact the landfills and transfer stations to see which one has compost available which you can get for free, bring your own shovel and containers. It might not be "registered organic" since it really is just the yard waste that gets collected and composted, it might not be perfect stuff (I often find glass and odd bits in it since it really is what people put out for yard waste collection) but I've grown stuff in it. It already has a mix of sand/dirt in it. Personally, I would do something more like lasagna gardening rather than trying to create a soil mix for the raised beds. I find that down here the more compost and organic matter you have, the more moisture you retain. Also, the more organic matter, the less the plants seem to suffer from nematodes. Now, all organic matter will break down and you will need to continue topping up the beds but it will be cheaper than buying "organic" dirt. I have lots of raised garden beds (to me raised bed means built on top of the ground as in a mound but I do not have any "sides" on my raised beds as they make weeding difficult.) Now if you really must buy "topsoil" and want good stuff. Go to nursery centers (not any of the big box stores) and see if they sell it in bulk. I know there is a place close to me that has big piles of bulk mulch and compost and probably soil of some sort. It will cost you so you are better off getting a good look at what they are selling before you agree to a price.