Google for ~ buy online "indole-3-acetic acid" produces about five sponsored links. I personally prefer Rootone® because it has a fungicides. Search for ~ rootone.

If you have high speed Internet you might want to visit "You Tube" web site, search on "propagation" and view videos by Dr. Fred Barnes of Texas A&M University. There is an interesting presentation of various hormones and their uses.

Hi There! Indole-3-acetic acid is an active ingredient in Schlutz "Take Root". I'm guessing it is also an active ingredient in RootTone. Both of these products are available at any place where packaged soils are sold. The name of that hormone was a mystery to me, too, until I read the labels carefully. I bought mine at a Fred Meyer store in the Gardening section. SAM