Where can you find a non-military large sturdy collapsable canvas bag in San Francisco?

try rei.com

yes, thought of that. also, inexpensive would be a desirable attribute. (although rei seems to be very high-quality which is good) goodwill? salvation army? any warehouse-type places? sports stores?

Why non-military? Surplus is probably the best way to get durable & cheap =)

i agree with bpeoples.