Here a photos of both kinds of latches in our Trade Wind. There is the original plastic one as you have. The catch that you are looking for is no more than a piece of metal with a bend a little more than a right angle to catch the latch. I like you had a few broken latches when we first got the trailer. I of course wanted to replace them with the original. However, the price I thought was unreal so I lowered my standard a wee bit. The cabinet latch pictured works well. It looks much more large and cumbersome in the photograph than it actually is. I bought it (them) at Orchard Supply Hardware.
Neil and Lynn Holman
Kirk Creek, Big Sur, Ca. coast.
1966 Trade Wind
1971 Buick Centurion convertible
1969 Oldsmobile Ninety Eight