We recently purchased a new diesel pusher, and I was a little disappointed to see that it too didn't have a luck for the rear access panel. Then, though, when I studied it, I realized that most things like the oil dipstick, trans dipstick, coolant reservoir could be reached with a little difficulty right through the slots in the rear access door. So I gave up on the lock issue.
Of course, we keep our motorhome stored in a locked garage in our backyard so that gives me a major advantage over you who keep yours in a storage area. I realize I am very fortunate to be able to keep our motorhome on our property.
Ed