The GPUSB guide port interface adapter plugs directly into a USB port on your computer or a USB hub attached to your computer. Using an RJ-12 cable, the adapter connects to the guide port of your telescope mount. This guide port interface uses optocouplers to electrically isolate the computer from the telescope, eliminating a possible source of electrical interference. This interface adapter requires no external power source since it receives its power via the USB cable.
Asking $60 plus postage
http://www.store.shoestringastronomy...roducts_gp.htm
Regards Paul