Here is my interpretation of a simple and cheap rod leash.
It needs to be simple, corrosion resistant, strong, and inexpensive. Everything but the bungee was purchased at Home Depot.
Here is what you will need:
3/16" bungee cord ($9.50/50 ft. on eBay)
paracord ($4)
plastic snap buckles ($0.99 for two pairs)
plastic S-biners ($0.99/ea.)
lighter
tape measure
1/16" SS wire
I began by making a lanyard, which has a female snap buckle on one end, and a loop on the other. The length of the loop can be adjusted to fit your needs. The plastic snap buckles came with instructions on how to make the lanyard. It's about as easy as tying your shoes.
I made up some DIY stainless steel hog rings out of 1/16" SS wire.
After approximating my shock cord length, I attached a S-biner to one end, and the male snap buckle to the other. Then compress the SS hog rings around the bungee.
That's it! The loop end of the lanyard can be modified to attach to your particular rod/reel. It can be easily looped through reel clamps that have a ring. Velcro could be ran through the lanyard loop for attaching the leash to the rod.