@Niki318 One dresser appears to be visible in the mirror on your listing's lead photo. I can't tell what kind of handles it has, but they don't seemed to be designed to be compatible with locks. I think any system you could rig up on that thing would look weird to guests.
On the other hand, if that dresser could serve a different function elsewhere in the house, you could move it out of the guestroom and replace it with a storage unit with a built-in lock. For that matter, the room seems to have a bit of space to spare, so it might even be able to fit both.
Another idea would be to install a lock on the walk-in closet and leave all your stuff in there. You could offer an external wardrobe for hanging clothes alongside the dresser.
Many possibilities there, but I think they all point toward investing in one more piece of furniture.