heavy duty stretchy beading cord, fabric

Hi I'm kind of new to beading and I'm trying to create this new design I
came up with. I am desperately trying to find a heavy duty beading cord
that's stretchy and also more of a fabric than neoprene or platic like. but
it still needs to be thin enough to fit through the bead holes. Can anyone
please help me? I would greatly appreciate any advice given. oh I would
also need to know the best way to knot what ever is suggested . Thank you

Andrea Manella ndd1"at"ptd.net