Finding the chemical components is increasingly difficult owing to hazmat fees and restrictions by suppliers, viz. many will no longer sell to individuals and require a Dunn & Bradstreet listing to open a commercial account. The cost of quality components is skyrocketing as well. Yes, there are alternative formulae that work quite well (see threads posted here), with the caveat that these are not official chemistry and cannot therefore be guaranteed to produce the same level of archival result. That said, in my experience the results are sufficient to expect my decades-old negatives to outlive me by a considerable amount.
Many of the formulae given by Dignan address long discontinued materials. Today, only C-41 and E-6 remain in the market and it is not necessary to seek out a copy of Simplified Color Processing Formulas. Bear in mind that many of the 3rd party chemistries, e.g. not Fuji and not Kodak, are in fact alternatives to the official processing chemistry.