Here's a picture of my personal bag with the longer straps sewn on and a screenshot of Indy holding the longer strap.
I created a chipboard template using one of the straps from my bag.
I punched hole into the end of the template and used a pencil to mark where the holes go on the leather. The second to the smallest punch on the hand tool matched the size holes in the original strap.
I scanned the end of the original straps to see where the stitching would go.
In Illustrator I lowered the opacity of the scanned image to 20% and on a separate layer created the stitching artworks.
After printing out the artwork I used 4 pushpins to hold the pattern in place on the leather. I used a leather awl to punch the rest of the holes into the leather. The center of the white areas between the black dashes are where the holes are punched. The black dashed represent where the thread would show.
Here is how the holes looked after the punching with the awl.
Here's the finished strap ready for paint.
I mixed various colors of the acrylic paint until I got close to the original color. You can see the various different shades of samples on the original short strap. I painted 1 coat of white and 2 coats of khaki olive. I used fine grit sandpaper to distress and expose the white similar to the straps in the movie. I distressed the left strap more figuring from the way Indy carries the bag one strap is used more. I followed up with 2 coats of Eco-Flow satin clear leather dye sealer on all sides and edges.
This is my reproduction Mil-Tec rucksack with the longer straps sewn on. I will use a little brown shoe polish to darker the white waxed Tandy thread. I used the two needle saddle stitching like I did with my label.
If there's any questions I'll try to answer them and add it to the tutorials.
