This past week I was sitting in another Ranger and it didnt have a locking glove box, I remember thinking how that was strange.
I wish I could remember whos truck it was, I think it was my boss's '98, I'll take a look tomorrow.
Anyways If your truck dosn't have one just swap one out with a locking one from a truck at the Junk Yard,but then again you would need the key for that.