From the pictures I could find, it appears that at least some of the entry doors use standard RV lock sets. There are a number of replacement lock sets available. Tri-Mark makes a bunch of the OEM lock sets with deadbolt and locking latch. I think there's only a handful of unique keys and many use the same key.
There are a number of electronic and/or wireless lock sets available as well. AP Products and RVLock brands are readily available on Amazon among other places. I believe RVLock claims some uniqueness in the keys, but I'm not sure how much. The "deadbolts" for all of the locksets are pretty flimsy.
If you're looking for something more secure that just drops in, I'm not sure there's a lot of offerings, but lets face there are usually a lot of entry points that are at least as vulnerable on an RV or horse trailer.