Take a look at the SX-880 tuner mute ckt! It derives the mute control from the PA-3001 detector, passes to the transistor switch, Q23 which switches the two jfets Q21,22.
Yes it is a bit of work to do, if you can not get the original part. But the easy part for you, is that the design is done in the SX-880, so all you have to do is copy it.
Suggest to buy a component header to replace the PA-1002-A and put the components on a prototype board.
You will have to add the buffer as was done in the SX-880 Q6,7 and wire up the the de-emphasis filter at the o/p of the PA-1001-A. You do not need the de-emphasis selector and just hard wire to the de-emph that you need for the US, 75us, C55,56 (11nF)
Actually, any n channel jfet should work since all that it is do is switching between pinch-off and IDSS(0V Gate-Source)