Grow them yourself or learn to ID them and go hunting. I haven’t bought shrooms in over a decade and I take them once every year or 18 months. I picked what ended up being 4 dry ounces in one day some years back. I was giving away to anyone who asked. Psilocybin-containing mushrooms grow basically anywhere where there (pick two) cows, people, grass, pine trees, cultivated lawns, hardwood mulch, rhododendrons, azaleas and college/municipal grounds with tropical to temperate climates.

You need to be extremely careful and ideally have a knowledgeable person help you until you really figure it out because there are mushrooms that will at best ruin your liver that look very similar to the ones you want in most of the places where the good ones grow. All Europe and the west coast Psilocybe cyanescens grows gregariously in big patches, sometimes intermixed with Galerina marginata, which will fuck you up in a death kind of way, not a fly to space kind of way. They look very similar, but are readily identifiable in the field. If you’re in the US south and anywhere near cows, you’re in luck - Psilocybe cubensis readily grows in cow patties and it’s damn near impossible to get a wrong ID given the circumstances.

Just order a grow box online.

I won’t link anything but should be trivial to find a store which sends ready to grow boxes.

In my experience they rarely get caught and because it’s not actually shrooms yet, they’re not even illegal everywhere.

You wet the box and then place it in a large plastic bag that comes with it and rolls as a sort of tent on top of it. Then just open it every day spray a bit of water.