The one thing fj12ryder didn't ask, is there a number like 751 on the head of the key or on the face of the lock core?
There were two primary keys in the early 90's, 751 and the other one has slipped my mind. If you can access the inside of the cabinet door, it is easy to remove the entire lock with either a wrench or a screwdriver depending on how the lock is held in place.
These locks are not sophisticated, but if you cannot unlock a cabinet, a locksmith can open it in a couple of minutes usually.
Go to TriMark, Camco or RV Designs and look at the locks available, or go to a RV dealer parts department and compare what you have to what's available and then pick one that suits your needs.
Ebay has literally hundreds of ads for cam locks that can be used. Don't fret too much about keeping the contents safe, most cabinet doors are easy to force, buy quality(TriMark) or anylock you are happy with.