You could swap a speedo from any other 92-95. Only problem is that your odometer reading will change. Are you sure it's not the sensor?
Si/EX clusters are identical and interchangeable with the VX cluster except the redline is marked at a higher RPM. You could even put in a non-tach cluster from a DX and it's plug and play. But just swapping your speedo only is your best option and it's not hard at all.