I might be able to assist. I'm in Melbourne, Australia and own one of the RAAF's old D4 Mk II Link Trainers, A13-157. I do have some spares, including a single electric fuel gauge, green and white lettered. It's serviceable.
The unit is essentially an electric motor - driven timer. A key is used to set a quantity of fuel on the gauge. When the tank in question is selected, the timer gradually runs down to E. When it hits E, a set of contacts open and the fuel warning light on the instrument panel is illuminated. If a tank containing fuel is not selected within a few seconds, the trainer 'crashes' (shuts down).
First row down in the photo, fourth box across to the right, third instrument from left. Not a good image of it, but all I have to hand at the moment. Unfortunately it's only one and you need two, but it's a start.
I'm always looking out for D4 bits - have a few things I'm trying to locate. Drop me a note and let's discuss.