I couldn't find that hippogriff of a bag anywhere! Surprise, surprise... cue pout.
I sound like Bratty McBratterson, don't I? Well, I'll admit to being a demanding, neurotic control freak, but I think I (sort of) manage to redeem myself by being willing to work for the things I want -- and boy, when I decided to make my dream bag myself, the process turned out to be work. Seriously, this
However, for about $30 in materials (blood, sweat, and tears are free... provided they're your own, of course), I walked away with a totally custom -- and customizable -- wearable work of art. Poor rivet planning aside, the bag was not that difficult to construct; if you have some basic sewing skills, then it should be pretty easy to make, as you don't even need to finish off edges when working with leather.
- Cut leather pants into strips as long as your desired bag is tall.
- Sew strips together lengthwise until desired bag width is reached.

- Follow instructions for constructing a lined zippered pouch... only, y'know, use your own measurements.
- Use leather scraps and a rivet setter to attach a D-ring anywhere you'd want a handle to be.

- Fashion straps out of leather and secure to lobster clasps with rivets.
- Clip straps to different D-rings to achieve a different look! Here are some examples in backpack mode, foldover mode, tote mode, and crossbody hobo mode.