It may be worthwhile to bring a couple packs of these;
http://www.mcmaster.com/#92401a643/=tg77b
The actual hitch pins like this have a built in handle and a chain to keep the keeper attached.
We had pins with keepers like what we are supposed to use this year, and they would often become unsprung and then bounce out.
Anecdote. I was once hauling a manuer spreader back to our farm with one of these pins. I hit a bump, it can loose and the trailer passed me going down the hill. Not good.