The brand “Mykos” is straight Rhizophagus Irregularis, and relatively cheap.
I should clarify that while I’ve seen the white paper for Mammoth P showing a symbiosis between the four species, I am purely speculating that it might also be the case with these long-list innoculants. I’ve seen no evidence to support that, and it could be just marketing like you were saying before.
An anecdote that might be relevant:
The first beneficial bacteria product I ever used was called Quantum-1 and it had a list of easily two dozen different microbes. Within a couple years the list had dwindled to ~4.