well the knob (only one knob turns on and off for cold and hot) is a Delta the HD worker told me. could not find the exact delta knob and to add to it, the screw that holds the knob..broke off its so corroded. The whole contraption is a Powers brand. the circular plate on the tile wall says that name. im not handy with plumbing. whats the best way to fix this? I cant find Powers brand anywhere. am i better off going to a regular hardware store and paying more but getting more what i need? thanks.