I bought a 10' stick of closet dowel at Home Depot, cut and sanded until the end was a sharp point, and plasti-dipped the other end. I *** it in the bottom and use a small loop of rope around it and a cleat. You want the pin/pole/anchor to be able to slip up and down as the boat rises and falls in waves or as you walk around. If you attach it rigid to the boat it tends to pull out of the bottom.
I have about $20 in it, maybe an hour worth of work, and store it inside when not in use. Been using the current one for three years and still have plenty of life left.