I finally went to Kraynak's and asked about the large-grain vermiculite that we were told about during propagation class. Someone said Kraynak's had it... t'aint so!
Kraynak's buyer showed me his stock of vermiculite: small bags that are available everywhere and huge bags probably only carried at nurseries.
However, they were both the small-size grains and when I said I would check again in the spring he said it was the only grain size/texture he had ever carried and would remain so.
If anyone knows where else to get the large-grain vermiculite please leave a comment or post to the blog with said source.
Perhaps I will try to contact the propagation presenter and see where he gets his. Let ya' know the outcome.