The pants belt is a WWII Army style cotton web belt used to hold up his pants. The web belts changed slightly during the three movies. In Raiders Of The Lost Ark and Temple of Doom the web belt is dark brown and in Last Crusade the webbing belt is a light brown/khaki color.
The gunbelt was basically the same in all three movies - however the whipholder was permanently attached to the gunbelt in "Raiders" and in "Temple". In "Last Crusade" the whipholder was slid on.
The gunbelt is 3,8cm wide (1,5 inch), and is quite ordinary. Noel Howard at M.B.A. had one but as of September 2003 M.B.A. closed down. Texas Action Gear has some good gun belts so try there first.
The brown webbing belt is rather hard to find, but the khaki belt can be found in any Army surplus store cheap.($2.95 for mine)
All You need to do is some distressing with fine sandpaper (grain 120), and maybe 2 - 3 times washing (without the buckle)
My gunbelt is from walmart and doesn't have the round buckle, but is otherwise pretty acurate. my pants belt is from the local army surplus store and has an inacurate black buckle but it holds my pants up!