Likely a combination of machining and coining the hinges would get you the result you are looking for. Efunda gives a figure of a million flexes possible for that type of hinge. The final aesthetic of the part in plastic would the thing to work on. You could get a hold of some of the Tectonic Toys hinges to quickly experiment with.
If you look for sheets of plastic to build prototypes from, Crown Plastics supplies a PE material used in sports that is likely to be offered in different colors and the approximate thickness you are looking for. DuraSurf.
http://www.crownplastics.com/catalog/index.php?cPath=26&osCsid=0f9d8d105b7e40320a7a6a7c7d3c7c34
Leather bags have combinations of dyed and burnished edges, with most synthetic ones seeming to be a roller applied thick coating to seal the edge. This looks like a pain to apply, and requires the thickness of the material to pull it off.
I could imagine, ( but have never seen ) an application of bead of two part PU that could encapsulate only your edge, however, robotic and probably left to a huge company to figure out first. PU’s can be formulated to set up in seconds.
Athletic shoes are the height of synthetics, the cleanest look is the latest generation of Nike et al. using laser cuts and laminations, the lasers melt and seal the edges perfectly with no fray, that would be the simplest thing to prototype.