I love Indiana Jones's famous bag, but the last thing I need is yet another mid-size satchel. I've been looking unsuccessfully for another small purse to replace one that's falling apart... so I decided to combine the two!
In the movies, Indy's bag is a World War II British MKVII gas mask bag with the cloth strap replaced by a leather one. You can still buy these as military surplus, and there are a few prop replica makers that sell them. According to an Ebay listing for a vintage MKVII, the dimensions of the original bag are approximately 10" x 10" x 3".
This half-size bag will be 5" x 5" x 1.5", though you could also scale up the pattern to make a full size bag. It is big enough for a phone, coin purse, and a wallet, with just a little room to spare. I have left off the bottom drain vents and the round circular thing on the side of the original, but these can be replicated with grommets and the right button.