I've had good luck poaching these sorts of things from several sources:

1) MEC online gear swap, or the in-store gear swap if you can figure out when it is
2) Thrift stores and sports replay stores.
3) Campers Village (you have one in Calgary) has lots of hardware/webbing/straps parts and
bits in their sewing/repair area that you can use to adapt or make new things.

You may find that often a small daypack or bookbag with decent suspension can be used
to tear stuff off for a starting point - I did this when I wanted a small compression sack for a bag that would also work as a daypack, and just sewed it together myself. I'd just look for
old packs that have a suspension like what you want and get out the scissors and seam ripper.