You can change to lcd if you know the make of controller, should be on the casing somewhere.
Or you may have to get new controller and lcd as a pair the only issue is with a new controller is whether wiring and connectors are the same so may need some fiddling about.
Or simply for £15 - £30 get a 25mm x 40mm (approx) wireless cycle computer, Cateye, Sigma or Lezyne and plonk it on the bars uses a simple receiver on the forks and a spoke magnet (both use a CR2032)