STARTECH StarTech.com 4 Port USB to Serial RS232 Adapter - DB9M - RS232 Extension - Serial to USB (ICUSB2324) - Serial adapter - USB - RS-232 x 4

Got more serial peripherals than you do ports? Don’t sweat it, StarTech.com has the solution to your problem with the ICUSB2324. It equips your system with four RS-232 serial ports while taking up only one USB port! Connecting devices like serial modems, GPS receivers, serial printers, and PDAs has never been easier.
Perfect for laptop users, the ICUSB2324 is light weight and compact, so you can take it with you when you’re on the go. As well, the unit is fully plug and play compatible, allowing you the flexibility of hot swapping your serial devices without rebooting.