Instrument cluster board

I am looking for an instrument cluster circuit board for a 1990-525i. This cluster is a two part assembly: one holds the gauges and the other holds the board which receives the inputs and controls the gauges. I checked the cluster's input signals: RPM/speedometer/temperature/fuel consumption/fuel level and they are all OK. Only the vehicle speed gauge records the correct speed. The others don't work. If anyone has had this problem and has changed the cluster, I would like to know were he/she bought it.