replacing lock on camper door?

[ScouterMom]

the door and latch/ handle on my 73 starcraft work fine, however, I did not get a key with it and can't lock the camper.  I'm going to have to work on the door anyway, as the weatherstripping around it is shot, and the interior ply is warped.

can I replace the key cylinder with a locking one from a screen door?  where else could I look for a way to replace the lock?  or would I be better off just putting a gatelatch and a padlock on it?  with a 35 yr old camper, I'm not too worried about security, more about someone just passing by in a parking lot & flipping open the door, or the door popping open on the highway. If someone REALLY wants in, they're not going to find it hard to get into that thin shell, anyway!

Also, anyone know of an inexpensive place to get replacement roof latches?  one of mine has been replaced, the others are very rusty and stiff.  I notice the newer one has a loop to pass a padlock thru, too.

[dbaldree]

Dose the lock have numbers or letter on it?