Buy some rope and jump it ...
Seriously, go to your local home improvement store. They usually have reels with different lengths and thickness of rope. I have a couple different thicknesses - use a thicker one if you want to work the arms. If you get real rope, ask them to tie off the ends. If you get "plastic" rope, burn the ends to prevent fraying. Real top works best - doesn't tangle easy and it's cheap.
Worked for Rocky...
Pro Kennex 7G, Head Rip Control 17 @ 58lbs, rubber band dampener, Tourna Grip.