Autodesk has a number of options that might suite your needs. Autodesk SketchBook Pro 6, SketchBook Express, SketchBook Copic Edition etc. They are available on the MAS and Pro is available on audodesk's web site.
I don't draw (much or well), so I can't say how similar they are when you get down to using them for "real" drawing, since I just do stick figures and scribbles.