More than a physical transition, USB to Serial cable converters emulate the functions of the Serial port hardware. Useful for maximum system flexibility. Just plug it in to your USB port or USB Hub and it maps itself to a "virtual" com port. Ideal for laptops that don't have serial ports.
Serial to USB Converter Cable: USB 2.0 to DB9 Male (USB2/DB9M), PC and Mac Compatible (Color may vary)
USB to Serial Converter- USB 2.0 (USB 2.0 to DB25 Male)
Tripp Lite series RS232 to USB Adapter Cable with COM Retention (USB-A to DB9 M/M), FTDI, 5 ft. (1.52 m)