StarTech.com 2 Port 16in DB9 Serial Port BRacket to 10 Pin Header - DB9 bRacket - DB9 Header - Serial Port bRacket (PLATE9M2P16) - serial panel - DB-9 to 10 pin IDC - 40.64 cm

Add two extra serial ports to the back of your PC, from your motherboard. The PLATE9M2P16 Dual Port Serial Plate adds two DB9 serial ports to the rear panel of a computer, connecting to two IDC10 header connectors on the motherboard.
Please refer to this product's Technical Specifications to ensure compatibility with your motherboard.