Trader Vollodos:
You must travel far from the village to find the fungus. They grow in the deep southern region of the Dark Forest, and also near the School of Dark Arts. You can get the Spore Sac by killing the fungus, but sometimes the Spore Sac explodes when the fungus is killed, so you will probably have to hunt many fungi.
Gather ten Spore Sacs and bring them back to me. Your payment will be more than fair, so do not worry.