This should not be too difficult. A 1k ohm resistor at 1mA will only drop out 1V, which is about the resistance of an analog meter.
So you could do this with a 1k from ground to the Ge transistor emitter and an analog input pin, and the collector of the transistor to 9V.
If you want or need better resolution, you could put an Op Amp in there to multiply the voltage x4, so at 1250uA there'd be 5V into the Arduino.