Near the port will be a voltage/ampage raiting, and a plug diagram. You will see these same diagrams on AC Adaptors sold commercially. You absolutely must match the voltage and plug (or get an apdaptor for the plug), but the amperage doesn't matter, as long as it is at least as much as your monitor needs. As for where to get them, your best bet it just to call up the LCD maker, or find a laptop that uses the same adaptor and get it online. It is possible (and fairly easy) to build your own, but NOT reccomended unless you have some expirence with electronics. These AC Adaptors are *NOT* cheap.
-Chu