Se você não se importar em gastar algum dinheiro, poderá sempre comprar um Matrox DualHead2Go
Matrox DualHead2Go is an external multi-monitor upgrade that adds up to two monitors to your notebook or desktop computer. Ideal for business and professional users looking to increase their productivity with a dual monitor setup, this small box lets you run different applications on each monitor or view one application across two monitors. DualHead2Go is available in DisplayPort, Digital, or Analog Editions.