It was long past time for a new one.
I didn't use a pattern. I didn't want a complicated project--this really only took me an hour or two--and I liked the shape of my old bag, so I just measured the various rectangles and copied it. Then I cannibalized the top and bottom supports and the shoulder strap to reuse in the new bag. (The original bag has a little briefcase-style hand carrier, too, that you can't really see in the photos, but I left it off the new bag because I never used it.)
Speaking of the buckles, they're actually reused from old bike helmets. They're a bit smaller than what I initially had in mind, but I wanted two that matched and that's what I found. And they do get the job done.
Fabric: White canvas (dyed) from stash, so old I can't remember and am saying free
Pattern: Measured off existing bag
Notions: Shoulder strap and supports cannibalized from existing bag so free; two buckles and strapping from SCRAP, $1.00; one package Rit dye, probably $1.80 when I bought it
Made before: no
Make again: in the foreseeable future, no, but I guess if/when this one wears out, I might
Sewing soundtrack: ?
Total cost: $2.80