I never realized that I forgot to state sources of ingredients, maybe a mod can amend this info into the original post.
Red Pottery Clay - Joann's, labeled as Red Mexican Clay, sometimes labeled as Red Indian Clay too.
Plantex csm+b - aquariumfertilizer.com or greenleafaquarium.com
Potassium sulfate - K2SO4 - aquariumfertilizer.com or greenleafaquarium.com
Epsom salt - drugstore/grocery
Potassium nitrate - KNO3 - aquariumfertilizer.com or greenleafaquarium.com
Also I went through and checked prices, and if your buy your clay from Joann's, which I believe was about $10, and the chemicals from aquariumfertilizer.com (everything besides Epsom salts which are cheaper from the drugstore) which are $26 shipped. That $40 roughly, which will make make approximately 500 1mm balls+. Which is definitely cheaper than Flourish tabs.