I have a Upvc front door with lever handles inside and out. Unfortunately our husky now knows how to open doors and has started letting himself out. I don't like locking the door because kids, postman etc. tend to come and go during the day so I'd like to replace the inside handle with a knob - which will be sufficient to bamboozle the dog but useable for humans. Does anyone know where I can source such a thing? All I can find are levers and pads.