go to the stereo shops behind citibank in blue area, they will fit an original CD player/changer AND a keyless entry system/alarm for a much lower rate than the dealership.
the alarm/keyless enty system will be cheaper and if it breaks down it'll be cheaper to replace/fix too. my advice is to get an original steelmate system (not a chinese replica) as they have so far been very reliable in the rest of my jap cars.