I have a few ideas making gear using nylon webbing (firewood carrier, modify vest, sheath, etc. ), but stiching it is a bitch. Been thinking about one of those hand held sewing machines, but don't know if they are strong enough.
If you are serious, you may want to look into an industrial machine.
For onesy twosey projects, lay it all out, then take it to a shoe repair shop. Most of them will be able to handle the stitching no problem for fairly cheap, as long as it is ready to do when you give it to them. If it still needs fitting and shaping, they may be less willing or more expensive to deal with.
I used a shoe repair place for some gear I had work done on.