I don't remember the site, but search on google/yahoo for junkyards/auto recyclers. There is a site that for like $5 will send out messages to all the auto-recyclers with what you want and they'll email you back with prices. The parts are usually guaranteed for 30-90 days which should be plenty of time to make sure its a good part.
Or you can buy one from mitsubishi, but it'll probably be expensive. You might want to call Buschcur or AMS as they may know of someone who sells/has one to sell... Shep Racing might know too.