I haven't made any bags from scratch, but I have customized my hiking bag by adding extra straps etc. I bought myself and old treddle Singer Boot Patcher
Beautiful machine. Unfortunately, as I am in a temporary place right now, the machine is in storage. I am reminded that I still need to purchase a few replacement parts for it. The bobbins wear after a while and it makes the unit skip stitches.
Totally non electric - beautiful.
My mom has an really old treadle sewing machine that she brought from Germany 35 years ago. Still works great.
Not sure exactly what you are looking for, gear wise, but here is a site with some plans for gear.
http://www.backpacking.net/makegear.html
The links are at the left side of the page. The page set-up is a bit different, but there's some good stuff here.
Here's an example bag for which they have plans.