StarTech.com 4 Port USB to Serial RS232 Adapter - DB9M - RS232 Extension - Serial to USB (ICUSB2324)

This 4 Port USB to RS232 Serial Hub lets you connect up to four RS232 serial devices to your Mac or PC laptop or desktop computer through a single USB port, as though the computer offered built-on DB9M serial connectors.
The RS232 Serial Hub is compactly designed to preserve valuable workspace, and is bus-powered to eliminate the need for an external power adapter.
A cost-effective solution that bridges the compatibility gap between modern USB-capable computers and legacy RS232 serial peripherals, this dependable USB/RS232 Serial Adapter hub is backed by StarTech.com's Lifetime Warranty.