Stone - Ian only gave the formula for stock A because all the Pyrocats have the same Potassium Carbonate B solution (the alkali):
Distilled Water 750 ml
Potassium Carbonate 750 g
Distilled Water to make 1000ml
Developers containing Pyro and Catechol generally need to be kept or packaged as two-part developers, with the alkali as part B because those developing agents oxidize quite quickly in an alkaline environment - particularly at the relatively high pH of Carbonate (which is the most common alkali system used in Pyro/Cat staining developers). Adding to that problem is the very low amount of preservative in a typical Pyro/Cat developer, which is a requirement for there to be significant imagewise staining.
The keeping properties of the separate A and B solutions are usually quite good when dealing with the most well known modern staining formulas (PMK, Wimberley, Pyrocat). Usually part B will keep for a long time. Part A shelf life varies depending on storage and how full the bottle is. To increase the shelf life of part A, some people prefer to mix Pyrocat in glycol.
There are a few one-solution Pyro/Cat developers. I haven't used any of that type, but if you want to experiment you might want to try something like Sandy King's "Pyro Uno" which has one stock solution (in Triethanolamine or "TEA") you dilute for use:
TEA 75 ml
Ascorbic acid 1.4 g
Pyrogallol 3.4 g
Metol 0.4 g
TEA to make 100 ml
There is also Gordon Hutchings's "Simple Pyro", one of his early trial formulas in the eventual development of PMK. He wrote an article about it recently in View Camera. It is again mixed in TEA and diluted for use. The formula is not set in stone but the "stock" solution is just TEA and Pyrogallol. You dilute it with water and add a pinch of Sulfite.