Yes, I second the comments on Michael Smith's formula. It can be found on their site michaelandpaula.com. The reason that Amidol gets the "bad rap" about rapid exhaustion is that the other formulas do not use citric acid. The citric acid stabilizes the formulation and hinders rapid depletion through oxidation. Artcraft Chemicals is less expensive and very accomodating on their chemistry. I have bought from both Formulary and Artcraft and so I have a valid point of comparison. Not that Formulary is "bad", please understand, but that I have found Artcraft to be more favorable.
If you plan on buying bulk chemicals (highly recommended) you will need something that will allow you to weigh in grams. There are ways around this but I have not used them so I can not comment on their accuracy.
As an aside, I learned yesterday that both Formulary and Artcraft were reportedly temporarily out of stock on Amidol...It appears that the secret is getting out. Good luck to you.