I broke my first pin on the boat ramp last weekend too! The boat was heavy with 3 inches of water in the hull from a leaky front hatch and very choppy conditions. I tried shoving the boat onto the trailer using the aka, but all that did was shear the nylon bolt. The spine-board haka kept the ama from folding in very much. Looks like a winch is in my future.
I have heard some folks carry a small phillips screwdriver that serves two purposes. It can be used to push out the broken bits of the rudder pin or aka pin and then it can be inserted into the space to serve as a temporary pin. Of course, if you hit something again, you will break something else before the screwdriver goes.
I am thinking of getting some 1/4 inch nylon rod instead of the nylon bolt that is currently used. It might provide just a little more shear resistance since it is not threaded, but should still protect the more durable parts of the boat.
http://www.amazon.com/dp/B0070ZG5WK/ref=biss_dp_t_asn-CC