I don't really have an Indy bag. All I have is this close-enough.
The strap is just something I found on another bag. The original strap was pretty much like the original MK VII strap.
With a couple of tweaks, this could be pretty much accurately resemble and Indy bag.
It's roughly the same size as an Indy bag only a bit bigger, I think (not sure if it is). It's heavy cotton-drill and very sturdy. I think the webbing attaching the strap to the bag is very durable.
What I put in my bag depends on where I'm going and who I'm with.
Things that are always inside the bag:
- emergency shoelaces on the front pocket
- mini hat brush
- small plastic bags for emergencies
Mall with Kids:
- my Canon S5IS camera
- extra batteries for the camera
- extra t-shirts for my kids
- band-aids
Mall w/o Kids or Meetings:
- a netbook (roughly the same size as an iPad)
On long trips:
- camera w/ extra batteries
- band-aids
- Salonpas (for body aches... dunno if you guys have that in your countries)
The back of the bag has an extra compartment... that's where I put the plastic bags and salonpas. Occasionally, I use that part to carry a water bottle for easy access.
The next thing I'm gonna put in there would be a small emergency LED flashlight.