Try looking online under crab pot making supplies. Also, if you know anyone down near the coast where crabbing is done, they can find a local source. When I needed some parts for mine, I ordered them but I can't remember from where.
If you are talking about unmade up bungee cord, some hardware stores may have it on rolls. I have see that one time, but haven't noticed any others, and wasn't looking for it when I went into those other stores.
Check out McMaster Carr industrial supply on the web, I am pretty sure they would have any kind you could think of along with any other snaps or hooks you might need to go with it. I looked all over for some polyurethane cord to redo the rod straps in my boat with no success and a buddy suggested MC, they had everything I needed.