The Indy-shirt was custommade for the movies, and are hard to find. Noel Howard at M.B.A. offered a replica of the shirt (as well as a lots of other Indy-stuff), but closed down business September 2003. If anyone knows if the are still in business i would love to know.
The shirt is a khaki safari shirt, with epaulets on the shoulders and two pleats on the sides of the shirt. A safari shirt can be found anywhere but the hard thing is to get one with the pleats.
L.L. Bean offers a "Cotton Poplin Long-Sleeve Field Shirt", (colour Tan) that is very close to the original. But this shirt does not have these "Indy-pleats" either.
But never doubt, my shirt doesn't even have 2 pockets, and no flaps on them either!
The Indiana Jones pants are made of wool. They have these hard-to find flaped backpockets.
They were originally cutommade for the movie, but You can find a great alternative at the great american company, L.L. Bean.
The most acurate colour is "Taupe". Only thing wrong is that they have a fixed crease so it will take a lot of wear to make them look really good. You can read more about them HERE , but they are very close to the originals. However Wested has just opened for sale of the Indy-pants too.