You can get a large bag of hardwood charcoal from Home Depot or Lowes. You can usually find small grade charcoal at aquarium stores of nurseries. I have seen it from time to time in HD or Lowes too. I buy it in the large bag for around $25 and use it for grilling as well as orchid mix. Years ago before bark became the rage orchid growers used charcoal alone as it was inexpensive and didn't break down.