Hey how do i get more toadstool. I tried to go to witchwood to see if they respawn or not. it seems they don't than I tried to buy them from the merchant she also doesn't sell them what should I do???

You find them in a variety of areas but they are limited resource. Reed's immune to the infection So he can protect the other party members at the cost of not attacking. There will be more in the Camp ground area, if you can make it there.