Thanks, a quick search for Nat.Cab.Co pointed me to
this one, which seems indeed the cabin door lock. Not big bucks, either.
Yep, changing all side doors locks (and glove box, you're right, I just forgot to mention it) would probably be more expensive.
I guess it depends on whether it's possible to change just the small cylinder inside or not.
You don't know which brand it is, by chance?