fbrieden,
Not duffle type but, Lowes and Home Depot both have gear bags. Synthetics I believe.
Carhartt makes a few sizes that seem to be popular with the iron workers. Not sure if they are canvas either.
What was I thinking?
Try Klein ... The guys that make the nose bags and pouches ...
http://www.kleintools.com/Cheers,
jb
Edit - Senior moment ...