Unlike Pianotuna, I like twist locks and suggest that you find a real electrical supply place and have them get out a pair (one male, one female) of L14-50 connectors. You want a cable clamp versions of both plug and receptacle. L=means locking, 14=means 4wire 120/230 volt, 50=means the ampere rating.
Because these are twist lock, when properly engaged, they will not come apart. But when "untwisted", they are much easier to uncouple than straight blade 14-50 connectors.
That is all that is used in marine service, but most are L6-30. There are a few boats built that are L14-50. And still fewer transient marinas with 50 at the dock.
Matt
