the craft lace or "gimp" as ive always heard it is pretty good but yes very stiff. but by heating it up by rubbing it fast with youre fingers, it will stretch a fair amount and be easier to use.
i agree with budy sanders on what the stretch cord or stretch magic is. it goes by both names.
also, at m local michaels, they sell a product which they call craft lace which is identicle to larva lace.
then theres plastic lace, which you can get a pack of about 100-200 strands of at the dollar store. this stuff is a thin plastic tubing, although its about as tough as the gimp. you can still heat it up to make it softer and more flexible though.