I got mine from here a few years ago. Looks like they are currently out of stock. I specified no master keys for the deadbolt or top lock and I also ordered slam latches and several CAM locks all keyed alike.
Now one key unlocks every door on my trailer and is completely custom.
http://www.rvlocksandmore.com/LocksK...43610-2006-1PK
You can then order more keys or locks with the same code in the future as well.