I've seen some newer "A"s have safes behind the wardrobe closet, behind the TV, in an entertainment center, and so on. The downside of a lot of these safes is that they are at best secure from casual use. However, a lot of them have a fire rating which may be more important than burglary.
I personally recommend "Fort Knox" brand of safes for small containers for items to keep secure. They have gun safes (which also double as decent strongboxes for cards and such.) They also don't have a fancy, electronic lock, but using a five-button Simplex lock which is a lot more reliable and has no batteries to run off. They also are pry resistant and decently secure. However, these gun safes are mainly intended to be lockers, and have no fire protection.
It depends on needs. Fire resistance is one thing. Burglary resistance is another, and you won't get both in something that is lightweight enough to be in an RV.