I am trying to complete a vermiculite source info page, before everyone needs it in the spring. I've found some good sources in the Midwest, Northeast, and Texas so far. I am still looking in the Southeast and Western part of the United States. International sources are also welcome! You can either contact me through GW or leave a comment on the link below. I'll compile and post a complete list. I also thought this might be timely for people traveling during the Holidays to be able to pick up a bag near their destination as opposed to their home.
Here is a link that might be useful: List your Vermiculite Source