Bob, you can go to a hardware store to get what you need. Heck, you can go to Lowes or Homeless Depot. You can also get the hardware that will let you make a nicely finished end, and you'll be able to select from both brass and stainless.
Something to keep in mind though...
Don't get too thick a rope. The thicker the rope is the stronger it is, but the less stretch and give it has. It also doesn't need all that high a weight rating.
Think about it this way... If you're in the water with your feet on the bottom and you shove your boat it moves, right? It doesn't take a whole lot of force to move a floating boat that only weighs at most a few thousand pounds. Even big yachts can be pulled to the dock by yanking on a rope attached to the boat.
If you want to read about rope, this is a pretty cool document I found. There is a lot more to rope than I thought. www.wescovan.com/catalogs/cordage.pdf
I agree with Eric that the stretch factor is key. I actually think in rough water though you could be in a situation where the forces on the rope are extreme. I was tied up next to a 310 SeaRay last year and a wake boat went past us. The SeaRay went up while my boat went down, and the line between the two snapped like it was a rubber band. The wave that was generated was huge because I remember looking up at his boat thinking it was impossible for it to be that far above me. If you REALLY want to read about it, check out this link to the US Navy Towing Manual. www.supsalv.org/pdf/towman.pdf
In it you will find a calculation for Towline Tension.
I would advise against using any tow line with metal clips, hooks, springs on the end because of the issue mentioned. If the line breaks under stress it will snap back at a very high speed and the metal could hit someone causing death or severe injury. A better option is a strap with end loops. You can find these at auto parts stores or online.