This is my same problem being in a rural area as well and my solution was to build my own with what’s available, sadly the stores will carry the ingredients to a good soil mix but sells the complete stuff with way to much wood chips and slow release fert beads which is just bad news for cannabis growing.
Feel free to check out this thread of my simple build that I’m still using that recipe and recycle my soil on my grows and has helped out many other growers on here to save money without sacrificing quality, I accompany that soil build with regular compost tea feedings and can hook ya up with some recipes there too if u feel like getting an air pump and a compost tea bag