NAVIsis, a Korean company, offers a Laptop Tablet which is a add-on for any laptop and turn them into a Tablet PC. The NAVIsis Laptop Tablet is priced at about $130.
The unit attaches to the side of your laptop LCD (or any LCD, we think) and plugs into a USB port. Presto chango. You are cool (unless you attached this to your preexisting tablet, in which case you are double cool)….The only drawback, no pun intended, seems to be that most screens could not take the wear and tear of constant stylus/greasy finger pressure.