I found lava rock at either H.D. or Lowes. It's in the landscape area with all the other stones and is red/clay colored. Decent size bag with mix of sizes good for orchids, just rinse it off well before putting in your pots.
Lorraine
Thank you Lorraine. I should have thought of that. Duh! Will run out and get stocked up and try to avoid being tempted by their ailing orchids.