Since you want both the material and to have it placed, you are looking for a Landscaping firm or possibly a small Excavation company, who can haul the material and place it.
If you want to move the material from stockpile yourself, or a dumptruck can get to where it can dump above the retaining wall (without putting truck load on it), then Mulch and Topsoil would be the Angies List Search the List category for that type of provider.
