if you want something that's going to last and not fall apart look at the itronix gobook. Ebay usually has them used and they're mil-spec. They're not cheap like the run of the mill laptops now. They're perfect for tuning, touch screen, backlight keyboard, serial port.
Exactly which units are you referring to? The only ones I see on Ebay are the tablet versions itronix, and they do not have serial ports.
The laptops,however, do have serial ports... Not sure about them being touch screen though..