The problem is that the style your looking for are newer and are typically more expense to start with. I wish you luck though...If you do find one can you let us all know?
I think Asus has a netbook tablet convertible about to be launched.
Anyway I'm also looking for a convertible, but I only intend to get it in October which is good as the prices are always going down. The IBM ones are apparently built like tanks so they are bound to be expensive.