If the door butts a jamb(or wall) when it is closed, you can install a pocket door lockset. Fairly easy installation for the average handyman. They can be found at Lowes/Home Depot or local building supply.
ANYWAY, IT DOESN'T BUTT ONTO ANYTHING REALLY. IT'S ON THE OUTSIDE OF THE BATHROOM JUST ON A SLIDER. I WISH IT WAS IN THE WALL BUT NO. I WENT TO OUR DEALERSHIP AND HAD A LOOK AT ANOTHER HAMPTON AND IT'S EXACTLY THE SAME, NOT ENOUGH PRIVACY.
Seems to me you have basically two options. Get a larger (wider) door or make the door opening smaller. If there is no hardware around the door jamb, you could take a piece of oak the same thickness as the wall, stain it to matchand place it on the three edges of your door frame. Hollow core doors are faily inexpensive (about $60.00 or less for mahogany, $75-80 for Oak or Birch at Home Depot). Not sure though if your door is a standard residential size.