There are locksmiths and "key places"
A key place.. Can not help you.
A locksmith, can open the door, remove the lock, cut you a brand new key.
Heck.. He may even be able to do it given just some numbers he can nab either off the lock or the VIN of the trailer. (Though VIN is doubtful on that kind of vehicle)
True story: Had a man lock his keys in his chevy pick up... No spare.. Took him to a dealer, handed the dealer his driver's license, registration, 20 dollars, and sat back.. A few minutes later the dealer handed him back his paperwork (only the twenty had turned into two singles) and a brand new key. Just like that. They made it while we watched.
Home is where I park it!