Try Rountree Plantation.

or you might call Renfro hardware in Matthews, they carry alot of stuff.

Call Protech Environmental (on Westinghouse in SW Cltte)...they supply LS contractors with a lot of landscape materials. I was in there last week for perlite and lime...thing I recall seeing 4 cf bags of vermiculite also. Not sure of the phone # off hand, but you can google it. they also have some good mixes from Daddy Pete's in Stony Point.