I'm lucky, I've been getting advice from the mother of a long time friend, who's been a seamstress for a long time. She makes clothes and things, but also makes musical instrument cases and gear for firemen. The cases are these cordura/vinyl arrangements, some of which have metal skeletons, that are meant to protect 25,000$ string instruments, and they would put most messenger bags to shame in build quality and material quality. The firemen gear is beefy as hell too, if it wasn't, people would die.

If you look at most bag construction, you'll see that they are very simply made, with simple sewing techniques. Thats why they are made by people who were messengers for a few years and decided to try out a sewing machine. If they were really that hard to make, they'd be made by people like this old lady who makes crazy clothing that people trust their lives and most precious posessions to. The differences between these high end messenger bags are mostly subtle placement of things, and material quality. Because they are so simple, the devil is in the details. So the ability to make something beefy isn't really the question, its the ability to make something comfortable and intuitve, that is also beefy. They don't make their own buckles, they don't make the fabrics. Anyone can get 1000 denier cordura, and anyone can order buckles from ITW Nexus. The key is the small details that only someone who really uses that type of bag would understand how to place.

For materials, check with places that sell material for outdoor equipment, like seattlefabrics.com. I'm using recycled vinyl plus heavy duty cotton canvas, but I might try out cordura for another revision.

Anyway, making your own bags may not be for everyone, but its a fun project (almost as much fun as building bikes), and it can be a great way to get a serious bag for less money, that includes the exact features you want. Plus, you get X-tra hip points for having a bag no one else has.

peace,
sam