I live in South Carolina and I was ordering my DE from custom milling in Georgia. It was a fair deal but shipping was about as much as the purchase price. This time I called around just looking for someone who carried other products from Custom Milling. I found a feed store about an hour from me who ordered other stuff from them. They agreed to include in their next order a special order for me. 3 50# bags of DE. Their policy is cost+freight+$2.00. I paid $22.00 per bag. Way less than if I had ordered it myself.
So, my suggestion is, rather than looking for someone who carries DE, look for someone who carries other products from the closest supplier of DE.