If you are not looking for topsoil, fill dirt should be easy. Check with the contractors that are doing ditch clearing and excavating locally. Also, paving guys are usually looking to unload dirt as they are doing much of the ditch clearing as well. Just pay them for their time and travel. Just be patient and they will likely be able to help you out for a nominal cost. The trucking is the spendy part. Waving some cash at the county guys might get you what you need as well.

Mark Ryan Paving
Shane at Asphalt Artistry
Jim Noble Enterprises
Saylor and Sons