I can vouch for the Vigoro at Home Depot—same stuff I used. I used a full 2 cubic foot bag and just a couple of scoops from a second bag. The rest went into our garden along with new soil, peat moss, and other good stuff all mixed in the concrete mixer.
You might not need the second bag, but it’s relatively inexpensive and the bag itself is very lightweight, so I opted for two.
(Also, we now recommend Perlite over Vermiculite because it naturally repels moisture rather than absorbing it as the Vermiculite does…so it will cut down drying time for an insulated slab from 6 days to under 2.)