Heck I thought the inside would be the most difficult part about this project. There must be someone here at the site with expertise about leather bindings. Now on to google to see if there are online tutorials.
I have been trying to find out what the name of the blade is the Sam Winchester is holding on the DVD cover art for season one. Finally, I found it.
It is called the Klaww of Death Dagger. You can buy it for $40.00. Pretty good deal if you ask me.
http://truedge.com/cutlery/misc.shtml
Hope...
I may be able to save you time.
http://www.movie-gear.com/supernatural.html
I have talked to the guy that runs this website and the colt replica he has is not screen accurate...yet. Apparently he is getting an official license and will be available soon. Plus there are other cool props there...
I saw a trailer for the next two episodes yesturday and not to give away any spoilers, we will get to see a lot of the inside of the briefcase. I would recomend taping it.
If you want the exact one for cheap:
http://www.campingsurvival.com/hwclmebag.html
Its the same exact one on amazon but cheaper. This is where I ordered mine from.