I'm Trying To Find Parts For A Crawlor Tractor - Help Anyone?

My father just came in and give me this International Harvester Operator's Manual for an INTERNATIONAL 500 SERIES-C Crawler Tractor which he's going to buy from some guy but it needs a few parts (he says). He asked me to go into the net and find him a place where they sell parts for it. I tried, but no luck. [My old man - he doesn't know anything about computers nor the net. He thinks that I can just type in anything (click click click) and right away get whatever I'm looking for. And with just this little bit of info to work with. This really sucks!!! But he's my dad so...] Anyways, can anyone help me out? Please and Thank you.