We have an old house with glass door knobs. Our bathroom has one as well. curren there is no way to lock the bathroom door which makes guests uncomfortable. We see a keyhole but have no key. Could a locksmith make us one? Or we're Wondering if the only way to put in a lock is to replace the doorknob with a more updated one. if so, can anyone recommend a place to buy glass door knob with a lock? Assuming we're not handy we'd likely need a handyman to install