I've used one like this for 11+ yrs, with no problems. It isn't locking, but is very easy to use. Just pull out the swivel barrel end (spring loaded), and pivot up or down.
I am not a locking pin user, we remove the hitch head and lock to the trailer coupler. Never had a problem doing that, and hitch stays clean when we head out on the dirty, dusty mountain roads we frequent.
Link to one source: http://www.amazon.com/Master-Lock-1465DAT-Stainless-Barrel/dp/B000COX0MY/ref=sr_1_6?ie=UTF8&qid=1398188799&sr=8-6&keywords=trailer+hitch+pin+lock
