I tried to find a replacement in home depot and they told me it is a interior door thickness and they don't have a door in 1 3/8" with a dead bolt (I was told the "lock block" isn't big enough) and I could only replace it with an interior door. It's possible the builder got these custom thin doors built with dead bolts provision in them 20 years.
It's hard to believe this is really so rare because I have seen doors of this thickness with deadbolt in other houses; i.e. going into backyard or garage into the house etc.
But they recommended me to upgrade to a thicker door made for exterior, in which I would have to at least move the door stop or replace the whole door frame to acommodate the extra thickness. The latter seem like a lot of work.
The current door is structurally sound but the wood on the surface has wrinkled up a bit. Which is why I am looking for a replacement and possibly upgrade.
Any help is appreciated.