Some people claim it was Lipton's, but personally I'm leaning towards Campbell's....
Actually, after reading about all the interesting chemical and mineral species produced in space itself, plus what I know about reprocessing on planetary surfaces (gases, fluids, surfaces) (and also geological processes underground), I'd guess that the soup must have had components from all possible sources- relatively unmodified planetfalls would bring active metals and things like polyphosphates that earth itself would rapidly destroy, geological reworking would make petroleum-like polymers and ring compounds that could then be modified on the surface (I don't think you get them by space or normal surface reactions).
And let's not forget the role of radiation- cosmic rays, x-rays, UV (maybe from the original open cluster the sun was part of), solar flares, etc. (and earthly lightning actually produces free neutrons!), and radionuclides- lots more actinides in those days from exploded supernovae in the original cluster- these wouldn't have dissolved in the oceans the way they do today with an oxidizing atmosphere- but would have accumulated on beaches- self-assorting layerwise versus other minerals like iron, nickel, etc creating a reactive structure that might exchange materials up and down as the tides came and went (and when bodies of water dried up these would be available for more gaseous reactions). You get alphas, betas, gammmas, etc.
Even elements radioactively transforming can prompt chemical changes- if the new species doesn't 'fit' where the original was anymore- so can act as a kind of molecular scaffolding. The soup probably contained all sorts of organometallic compounds that could mediate reduction-oxidation reactions (we only have a taste of that remaining today, with metallo-enzymes, etc.
Unfortunately writers on this subject tend not to take the entire plethora of possibilities into account, but are squarely blindered within their respective specializations. Very much 'within their boxes'.
Jess Tauber