I bought a softball-sized Lion’a Mane mushroom at NaturalGrocer in my ‘hood. $14. It was actually iuite yummy but the price is enough to make anyone crazy..
You can buy them desiccated, I think, but have no clue about the efficacy.
Easy to grow, learn how. You can also find it on downed logs after a rain. Get sone oak logs, drill some holes and insert fresh Hericium in them. Give it some time and you will have some.