[Dan Nunn]

Just looked and this Dell Latitude D531 has one.

It can be had pretty cheaply on the Dell Outlet.

[Dan Nunn]

And just to make sure, Tech Specs on Latitude D531:

EXPANDABILITY:
I/O Ports:
Serial, docking connector, S-Video, IEEE-1394, 4 USB, VGA, headphone/speaker out, RJ-11, RJ-45, AC power, integrated microphone

[bigbob]

Chances are the serial port is connected via USB internally. The chipsets used in PCs today do not have actual UART hardware.