Westpoint MS ( http://www.marlyncer...amics_supplies/ This should be about a 1 hour drive for you
Also you might try this retailer in Morton, MS http://www.landovoz.com/ (central ms). They drop ship clay to me (same lb price and something like a $25 delivery fee for 2000 pounds ... cheaper than driving to get it). This should be about 2 - 2.5 hours drive for you.
Both of these are closer than 4.5 hours.
(I have no affiliation with either of these places, besides being a normal customer)
Thank you for the info - I should be able to find what I need without driving too far! The drop ship option sounds like a great option.