I'd check G.I. Joes first - they've had a lot of crazy Christmas deals going on... and if that doesn't work, check Home Depot or Jerry's... Bi-Mart has rope, but not a very big selection.... Fishing this weekend?? Matt suggested the Metolius... ??
Brent: RE: SEAT
I tried something on my boat that I have heard of, but not seen. I used a 2" web strap (take off from my larger boat winch) instead of rope. I have not used it much yet, but I do not have rope marks on my rear yet. I fastened individual lengths to a wood mounting strip with galvanized staples and epoxy. The strips (7) were then stretched via clamps and screwed to the outside of the seat area. It feels pretty good, but I have no experience on how well it will last.
Great looking boat.
Kenny Kent