We've used Nevron before for other WinForms charts and they were great - the product worked and the Tech Support was really helpful.
They seem to do surface charts (at least as I understand them):
www.nevron.com/Gallery.ChartFor.NET.ChartTypes.GridSurfaceChartGallery.aspx
www.nevron.com/Gallery.ChartFor.NET.ChartTypes.MeshSurfaceChartGallery.aspx
www.nevron.com/Gallery.ChartFor.NET.ChartTypes.TriangulatedSurface.aspx
(I tried to make them proper links but because I'm new I wasn't allowed to put in more than one)
