My Indiana Jones recipe is:
Headsculpt and Hat:
Hero Heads by Lonnie Hale (soft hat version)
Jacket: modified Dragon A-2 Flight Jacket Set
Shirt: modified from an Ultimate Soldier German Officer Uniform (Cassino)
Bag: Sideshow French M2 gas-mask bag, added leather strap.
This is not film accurate but I felt this bag had the perfect shape for an adventurer.
Gun Belt, Holster, and Whip Holder: handmade from Leather
Gun: I chose a Dragon Enfield Revolver but I think this is relatively unimportant. Indiana Jones seems to go though guns like they were candy.
Whip: Dragon Danger Girl Sydney Savage
Belt: Dragon in Dreams Charles Winstone
Pants: They are from a Dragon WWII US figure, I chose them for their color when compared to the shirt and jacket.
Shoes: Dragon in Dreams George Puller, they not 100% film accurate but they match the character very well.
It is important to point out Indiana Jones' costume varies slightly from movie to movie. You make like the design of a particular sequence or photograph and I would suggest starting from there.