I just had a quick look at the circuit diagrams for the TVs that you mention, and I reckon it would be worth giving the IR board from the BV1/BC1 a try. It’s a one-way IR unlike the earlier models (i.e you want an IR receiver rather than transceiver).
MX8000:
BC1/BV1:
I have had success swapping IR sensor between MCL and ML systems. In the majority of cases, as long as you get the +5V, ground and IR connections (1-3 above) then it works! You could probably even try a VX sensor or BS3 sensor if you have one.
I think that in the above examples, pin 4 is the sensor for the auto-contrast and 5/6 for the respective lights.
Of course whether it will physically fit is another matter!