I have a place called crazy harrys here...idk if it's in other states but I have seen a few in my state...they sell flowers ..shrubs...garden plants ...but they don't sell soil...I'll have to check with em to seemed where they get it from...
Damn that's insane man, where do you buy food??
It sounds like you do have some options though potentially! The only thing you might get screwed on is if your stores only carry miracle gro brand (they put synthetic fertilizers even in their base products). But a lot of people are wary of chemical Fertilizer these days so most stores will make a point to carry at least one non Miracle-Gro brand.
The Tractor supply store would probably be a good start. Ace hardware too. Any home improvement or large grocery store should have a gardening section, especially right now when the outdoor gardening season is starting. Any place that sells vegetable starts or seeds would be a great place to go to. They won't have bags of ocean forest, but they should have all the base ingredients to make your own organic soil.
Spaghnam peat moss. This comes in everything from 2.2 or 3.8 compressed cubic feet bales, and also smaller half cubic feet bags.
Perlite. I get 4 Cubic feet sized bags at a local landscape supplier for 20 bucks a pop (amazing deal) sounds like you won't be that lucky unfortunately. You should be able to get a hold of some cubic foot of half cubic foot bags though. If they do not have perlite but do have vermiculite, that'll do. It provides aeration differently, but it's still aeration.
Compost/worm castings...this is one of those well it would be nice but we can work around the lack of these if necessary. Anyway, worm castings. They are great, encap started adding worm castings to their line of garden products and that brand is carried in big box garden stores so you might find some, you might not. They can also get expensive. Definitely set up your own worm bin. I recently set mine up and am kicking myself for not doing it sooner. I didn't even have to order my worms online, the local bait and tackle shop sells red wigglers.
Compost however, you should be able to get a hold of some compost. Any store should have it. If they don't, call your trash service. Odds are they have a recycling program, and they also probably have a compost program. If they won't sell it directly to customers I'm sure they'll direct you to the landscape or garden supplier that they sell it to. If you have grass on the lawns of your city then there has to be compost somewhere!
That stuff should make up your main mix
1 part peat moss
1 part perlite
1 part compost
If you got worm castings I would just top dress with them unless you can get them for cheap. Then sub them in for the compost.
Dolomite Lime. Also sold as garden lime, or soil sweetener. Just don't buy hydrated lime. You don't need a huge bag but some garden center's sell it in huge bags. It's just for raising the pH in the peat moss, you won't need much. I mix in about 1 and a half Tablespoons per five gallons of mix.
That's your main stuff, you won't have to check the pH of your water and you'll have some fertilization from the compost and or castings.
Moving onto amendments, there are some that would be amazing to have, but odds are these might be out of your reach.
Get these if you can :
Kelp Meal
Alfalfa Meal
Fish bone meal
Oyster Shell Flour
Azomite
Granular humic acid
Bat Guano of all varieties
Those are in a perfect world though. You're probably going to have to settle. You should be able to find:
Bone Meal
Blood meal
Gypsum
Greensand
Chicken manure
Let me know what you can find and I can give you some soil mix advice! I've grown with all these things with great success!
